concurring in part and dissenting in part:
I believe that the Department of Commerce Appeals Board reached the correct result, and for appropriate reasons, and so I depart from the court’s opinion, though only partially from the judgment.
The Board considered the travel-time contract clause, found it to be ambiguous, mentioned the contra proferentem rule, but nevertheless decided the controversy on the grounds of equitable estoppel. The majority thinks it error for the Board to have taken this last step — once contra proferentem is found applicable, the result is thought to be mandated. I do not disagree that the clause was ambiguous or that it should be read 'against the drafter, the Government. But in my view the court’s position on equitable estoppel misconceives the nature and role of that doctrine, and its relation to the construction-against-the-drafter rule of contract interpretation.
Before examining the application of estoppel to this dispute, it is helpful to note two important characteristics of this principle. First, it is not a tool of contract interpretation. Although courts and other tribunals will sometimes regard the conduct of the contracting parties when choosing between the cusps of an ambiguity,1 this kind of conduct-analysis is *722distinct from that forming the basis of an estoppel.2 It is clear that the Commerce Board was not ascertaining the meaning of the contract by observing the parties’ behavior under it; rather, it was weighing events by the more exacting tests of equitable estoppel. The kind of conduct that gives rise to an estoppel must be appraised more strictly (the action or inaction must be relatively unambiguous, the parties must be unequally knowledgeable 'about the situation, etc.) because, as noted below, this defense can be imposed against a party whether or not its interpretation of a contract ambiguity is accepted by the court.
Neither can it be said that the contra proferentem, rule and estoppel are on a par in the hierarchy of legal values and analytical techniques.3 “Equitable estoppel is a rule of justice which, in its proper field, prevails over all other rules.” United States v. Georgia-Pacific Co., 421 F. 2d 92, 96 (C.A. 9, 1970). The reason for this pre-eminent position is organic to the nature, goals, and operation of the doctrine. “Equitable estoppel in the modern sense arises from the conduct of a party, using that word in its broadest meaning * * *. Its foundation is justice and good conscience. Its object is to prevent the unconscientious and inequitable assertion or enforcement of claims or rights which might have existed or been enforceable by other rules of the law, unless prevented by the estoppel; and its practical effect is, from motives of equity and fair dealing, to create and vest opposing rights in the party who obtains the benefit of the estoppel.” 3 Pomekoy’s Equity Jurisprudence § 802, at 180 (5th Ed. 1941). The principles of equitable estoppel are foreign neither to this court nor to the substantive law of government contracts,4 and we should not shy away from giving the doc*723trine full effect whenever a proper case arises. Paying due deference to this venerable principle of justice may require, as here, overriding the result indicated by a lesser rule (such as one of contract interpretation). But when a good case for estoppel is made out, I would not hesitate to put first things first.
Given the legal function and priority of equitable estoppel, I see no error in the Board’s consideration of this issue in spite of its earlier conclusions (the accuracy of which I accept) that the contract clause was ambiguous and the rule of contra proferentem applies. As stated above, the nature of an estoppel is that it overrides and cuts down other legal rights and claims, such as these flowing from the rule that a non-drafting party can charge its opponent with responsibility for a latent unclarity.
Utilizing the accepted elements of equitable estoppel, the Board sought to find whether the contractor had given the Government, to its detriment, reasonable cause to believe that the former was not interpreting the contract as requiring travel-time payments. The contractor had the duty (set forth in Article XI, quoted in the court’s opinion) to submit monthly bills “in the form of an itemized invoice covering all services furnished during the month.” (Emphasis added.) In proper context, silence in the presence of an obligation to disclose is sufficient to create an estoppel, and this contract, which puts the burden of claiming payments due every month squarely on the contractor’s shoulders, called upon plaintiff to inform the defendant of all items believed to be owing.5 I agree with the Board that “by not billing for travel time or even raising the subject until March 1970, the contractor can be deemed to have led the Government to believe that it was accepting the {Government’s] intended interpretation of the contract.” 72-1 BCA ¶ 9330 at 43,269.
*724In addition, the Board rightly found “detriment” in the substantial delay foreclosing the Government’s opportunity to sidestep an incipient dispute quickly and cheaply. “Had [H & M claimed promptly and regularly for travel time], the difference of interpretation might well have been revealed early in the course of performance, thereby giving H & M and the Government a quick opportunity to reach a mutual understanding or terminate the contract * * * .” 72-1 BCA at 43,270. It is unnecessary to speculate, as the court does, as to what the Government would have done had it received a prompt bill, early in the course of performance, for travel time. To find the detriment needed for estoppel, it is enough that the opportuniity for loss-avoidance was denied, as it was here. Cf. Ling-Temco-Vought, Inc. v United States, 201 Ct. Cl. 135, 475 F. 2d 630 (1973), discussed infra. On these bases, the Board seems to me quite right in holding plaintiff estopped from claiming pre-May 12, 1970, travel-time payments.6
The court, as I see it, puts the wrong construction on this administrative holding. The Board did not interpose the defense of laches, or any equivalent. This is not a case where delay in asserting a claim is considered so inequitable as to bar the demand, but rather, as the Board found, H & M’s affirmative conduct, by failing to include travel time in a supposedly complete bill, misled the defendant to its detriment, thereby precluding plaintiff from now recovering the travel-time money. And the Board, in considering the failure to bill travel time as raising an estoppel, did not (as the majority also implies) assume that II & M had a duty to inquire whether the Government shared its interpretation of the unclear clause. Instead, in the setting of the contractual duties created by Article XI, supra, H & M’s failure had the *725consequence of misleading the Government, lulling it into the belief that there was no interpretative dispute, and that travel time (for the months before the issue ripened) was neither claimed nor owed. Though the plaintiff may have had no duty to inquire, it did have the obligation not to lead the defendant astray.
Such misrepresentation by silence is reminiscent of the recent case of Ling-Temco-Vought, Inc. v. United States, 201 Ct. Cl. 135, 475 F. 2d 630 (1973). That plaintiff charged a Navy official with inducing it, by false promises and representations, to fund a contract overrun. The court refused to award damages on this theory, however, because shortly afterwards plaintiff learned of the falsity of the alleged misrepresentations, but nonetheless continued to perform the contract and expend money on it in total and unexplained silence, “knowing all the time that the Navy did not intend to reimburse it for such expenses and that the Navy thought and continued to think that the plaintiff fully agreed to that course.”201 Ct. Cl. at 145, 475 F.2d at 636.Similarly,H&M submitted bills, which it should have known the Government would consider full and complete claims for payment, without mentioning the significant matter of travel time.7
The Board also held that H&M was entitled to payment for the post-May period, likewise on the ground of estoppel— this time the defendant’s ox being gored. The court confirms this result, but only on the basis that the contract, correctly read, decides the issue. I agree that that is one proper ground, but at the same time I think that the Board’s view furnishes a.n alternative 'basis for the same result. After the emergence of the dispute over contract interpretation, payment of travel-time bills by authorized officials was sufficient in this instance to estop the Government from later claiming that travel time *726was not payable, on H & M’s interpretation, for periods after the payments had 'begun.8
For these reasons, I would affirm the decision of the Department of Commerce Appeals Board, both in result and reasoning, and therefore would deny both motions for summary judgment.
Kashiwa, Judge, concurs in Judge Davis’ dissent.See, e.g., Dynamics Corp. of America v. United States, 182 Ct. Cl. 62, 73, 389 F. 2d 424, 430 (1968) ; 3 Corbin on Contracts § 558 (1960) ; Uniform Commercial Code § 2-208.
Although the two legal principles are different and distinguishable, they both spring from the common-sense proposition that, at least in civil litigation, a person should normally be held to account for the plain implications of his overt actions, whether or not he privately harbors another view.
One important commentator views contra proferentem as a residual method, to be used “as a last resort” only after all other techniques of contract interpretation fail to resolve the ambiguity. 3 Corbin on Contracts 5 559, at 262, 268-70 (1960).
See, e.g., Pacific Far East Line, Inc. v. United States, 184 Ct. Cl. 169, 194, 394 F. 2d 990, 1000 (1968) ; United States v. Georgia-Pacific Co., 421 F. 2d 92 (C.A. 9, 1970) ; United States v. Hanna Nickel Smelting Co., 253 F. Supp. 784, 793-95 (D. Ore. 1966).
Since the contract was bid and paid on a man-hour basis, these bills were the only way that proper payment could be made. The Importance of the billing duty Is amplified by the fact that H & M’s method of paying Its workers departed, at least In large part, from Industry practice. See H & M Moving, Inc., DCAB-OAS-1, 72-1 BCA ¶ 9330, at 43,266. Thus, the only way the Government could have learned of H & M’s Interpretation, or the legal problems arising from It, was to be put on notice by a complete monthly bill.
The Board found that H & M first gave notice of an intent to bill for travel time around February 1970, that the first bill was presented late in April, and that the first payment was made on May 12 of the same year. It was not compulsory to decide the beginning and end of the estoppel period with mathematical exactitude, and the Board was within its discretion in selecting the May date.
As the Board found:
“Applying again the four elements required to establish estoppel, we find that by the time of the mid-May payments of retroactive travel time to H & M, the Government (1) knew of the facts regarding H & M’s Interpretation of the travel time provision, or enough of them to have put a reasonably prudent party on inquiry; (2) so acted, by paying the Invoices without question, as to give H & M reasonable cause to believe that the Government accepted Its Interpretation of the travel time provision; whereas (3) H & M was not Informed by the Government of Its intended interpretation; and (4) H & M had cause to rely and did rely on the payments as conduct justifying Its continuance to perform under the contract and to extend it to H & M’s detriment or Injury.” 72-1 BCA at 43,271.
It is now settled that the Government, as contracting party, may be estopped. The sole question unique to imposing estoppel on the contracting sovereign is whether the officials acted within their authority. The Board considered this issue at length and found proper authority, see 72-1 BCA at 43,271-72.1 concur in its analysis.
It makes no difference that H & M’s failure to bill travel time may have been the result of its own innocent error, because the Government, like any other contracting party, is entitled to rely on the overt and objective actions of contractors. Cf. Long-Temco-Vought, Inc., supra, 201 Ct. Cl. at 150, 475 F. 2d at 639.