Panhandle Eastern Pipe Line Co. (whom we will call Panhandle Eastern) owns properties which constitute a natural gas production, transportation, and marketing system. The system extends from gas fields in Texas, Oklahoma and Kansas through Missouri, Illinois, Indiana and Ohio and into Michigan. The City of Detroit and the County of Wayne, Michigan, filed a complaint with the Federal Power Commission alleging that Panhandle Eastern's rates on gas sold to a distributing company in Michigan for resale there were unjust and unreasonable. The Commission on its own motion instituted an investigation under the Natural Gas Act of 1938, 52 Stat. 821, 15 U.S.C. § 717, 15 U.S.C.A. § 717, of all of the interstate wholesale rates of Panhandle Eastern. Following extended hearings the Commission entered an interim order, here under review, finding petitioner's interstate wholesale rates to be excessive and requiring petitioner to reduce them on and after November 1, 1942, as to reflect, when applied to petitioner's 1941 transportation and sales a reduction of not less than $5,094,384 per annum below the 1941 consolidated gross operating revenues of $17,789,573. See 45 P.U.R. (N.S.) 203, 223. That order was affirmed by the Circuit Court of Appeals for the Eighth Circuit, one judge dissenting in part. 143 F.2d 488. The case is here on a petition for a writ of certiorari which we granted limited to the two questions which we will discuss. But before we reach them we must dispose of a challenge made by the City of Cleveland, as amicus curiae, to the jurisdiction of the Circuit Court of Appeals for the Eighth Circuit over the subject matter of this litigation. Panhandle Eastern sought review in that court of the Commission's order under § 19(b) of the Act which so far as material here provides:
'Any party to a proceeding under this chapter aggrieved by an order issued by the Commission in such proceeding may obtain a review of such order in the circuit court of appeals of the United States for any circuit wherein the natural-gas company to which the order relates is located or has its principal place of business, or in the United States Court of Appeals for the District of Columbia * * *.'
The petition for review stated that petitioner had its principal place of business in Kansas City, Missouri. That was not denied by the Commission and at no time prior to the entry of the judgment affirming the Commission's order was the jurisdiction of the Circuit Court of Appeals challenged. After the judgment of affirmance had been entered, however, the City of Cleveland filed a motion in the Circuit court of Appeals for leave to intervene and challenged the jurisdiction of that court on the ground that petitioner did not have its principal place of business in that circuit. The same objection is pressed here.