We are called upon in this case to determine the effect of an order entered by the Circuit Court of Cook County, Illinois, striking and dismissing a cause of action with leave to amend the complaint within twenty-eight days. Our analysis of applicable Illinois law persuades us that the order is not a final order and that the district court therefore erred in concluding that plaintiffs’ federal claim was barred.
Maria Angelica Gilbert and her daughter, Rosita, filed an action on June 6,1975 in the Circuit Court of Cook County seeking recovery against the defendant for alleged wrongful conduct occurring in January, 1974 in connection with an airplane flight from Miami, Florida to Santiago, Chile. On July 14, 1975, upon motion of the defendant, the Circuit Court of Cook County ordered that:
“. . . defendant’s motion to strike and dismiss plaintiffs’ cause of action be granted with plaintiffs being granted 28 days in which to amend their complaint.” [R. 19] (emphasis in original).
Rather than amending their complaint, plaintiffs filed this action in the United States District Court for the Northern District of Illinois under § 404(b) of the Federal Aviation Act, 49 U.S.C. § 1374(b).1 It is conceded that plaintiffs’ claim in both the Illinois court and the federal court was based on the same operative facts involving the same parties. The district court determined that the state court’s order of dismissal was a final order barring any further adjudication of claims arising from the same factual basis. Accordingly, the district court entered summary judgment in favor of the defendant on the grounds of res judicata.
*413It is well settled that the doctrine of res judicata can be invoked to bar a subsequent claim only if the prior action was terminated by a final judgment. See: Merriam v. Saalfield, 241 U.S. 22, 28, 36 S.Ct. 477, 60 L.Ed. 868 (1916); Premier Electrical Construction Co. v. Miller-Davis Co., 422 F.2d 1132 (7th Cir. 1970); People v. Harkness, 34 Ill.App.3d 1, 339 N.E.2d 545 (1975) . Further, an order is considered final if it terminates the litigation between the parties to the suit, and finally determines, fixes, and disposes of their rights as to the issues made by the suit. Peach v. Peach, 73 Ill.App.2d 72, 78, 218 N.E.2d 504 (1966) .
Illinois Supreme Court Rule 273, Ill.Rev. Stat, ch. 110A, § 273 (S.H.A.1968) provides:
Unless the order of dismissal or a statute of this state otherwise specifies, an involuntary dismissal of an action, other than a dismissal for lack of jurisdiction, for improper venue, or for failure to join an indispensable party, operates as an adjudication upon the merits.
In this case, it is clear that the Circuit Court of Cook County’s order of dismissal resulted in an involuntary dismissal with respect to the plaintiffs, and must be considered a final order by operation of Supreme Court Rule 273 unless it can be demonstrated that the order specifies otherwise.
In determining whether a particular order is final, Illinois reviewing courts look to the substance of the order, rather than its technical form. Browning v. Heritage Insurance Co., 20 Ill.App.3d 622, 314 N.E.2d 1 (1974); Bates v. Ulrich, 38 Ill.App.3d 203, 347 N.E.2d 286 (1976); O’Fallon Development Co. v. City of O’Fallon, 43 Ill.App.3d 348, 2 Ill.Dec. 6, 356 N.E.2d 1293 (1976) ; Peach v. Peach, supra, Martin v. Masini, 90 Ill.App.2d 348, 232 N.E.2d 770 (1967) . So viewing the order involved in this case, we find that it lacks finality.
The very terms of the order itself, striking and dismissing the cause of action with leave to plaintiffs to file an amended complaint, reveals a lack of finality and indicates that there is yet something to be done in the case. Further, no costs were assessed — a factor considered to be important in determining the finality of an order in Bates v. Ulrich, supra, 347 N.E.2d at 288. Moreover, the defendant did not seek the entry of an order by the Circuit Court of Cook County dismissing the case with prejudice for failure of the plaintiffs to file an amended complaint, as is the apparent practice. See: Campbell v. Harrison, 16 Ill.App.3d 570, 306 N.E.2d 643 (1973); Brainerd v. First Lake Co. Nat. Bank of Libertyville, 1 Ill.App.3d 780, 275 N.E.2d 468 (1971). In light of these considerations, we view the order of dismissal with leave to amend the complaint as within the “otherwise specifies” exception of Rule 273, and, hence, conclude that the order is not a final order by operation of the Rule. See: Stutzke v. Edwards, 58 Ill.App.3d 832, 16 Ill.Dec. 296, 374 N.E.2d 1071 (No. 76-571, 1978); Gray v. Starkey, 41 Ill.App.3d 555, 353 N.E.2d 703 (1976).
Because the state court dismissal order was not a final adjudication on the merits of the cause of action by operation of Rule 273, res judicata could not properly be invoked to bar the subsequent filing in federal court of a complaint based on the same operative facts. Thus, the cases relied upon by the district court and urged by defendant here, Hanson v. Hunt Oil Co., 505 F.2d 1237 (8th Cir. 1974) and Lambert v. Conrad, 536 F.2d 1183 (7th Cir. 1976), are inapposite because those cases involved prior final adjudications on the merits which were then raised to bar subsequent litigation under principles of res judicata. The instant ease more closely resembles Brainerd v. First Lake Co. Nat. Bank of Libertyville, supra, 275 N.E.2d 468, where a complaint was dismissed for failure to state a cause of action and additional time was given to plaintiff to file an amended complaint. It was not the order of dismissal with leave to amend but rather the subsequent order of dismissal “with prejudice” when plaintiff failed to file an amended complaint that was held to be a final order by the operation of Rule 273. 275 N.E.2d at 469-470. Similarly in Campbell v. Harrison, supra, 306 N.E.2d 643, the court found that an order striking *414a complaint with leave to plaintiff to file an amended complaint was not a final order but rather a subsequent order dismissing the case because the plaintiff did not file an amended complaint was a final, appealable order. 306 N.E.2d at 644-645.
Accordingly, for the reasons stated herein, the order of the district court is reversed and the cause is remanded for further proceedings not inconsistent with this opinion.
REVERSED AND REMANDED.
. 49 U.S.C. § 1374(b) provides:
No air carrier or foreign air carrier shall make, give, or cause any undue or unreasonable preference or advantage to any particular person, port, locality, or description of traffic in air transportation in any respect whatsoever or subject any particular person, port, locality, or description of traffic in air transportation to any unjust discrimination or any undue or unreasonable prejudice or disadvantage in any respect whatsoever.