The reason that the major airlines are given bandaid loans and allowed to refinance by the gov't. is that they are necessary to private, commercial, and industrial travel. Yes there are smaller companies who would love to gain some business from the Major carries. But, there's a few problems...

They don't have the ability to handle the same massive traffic. Equipment, engineers, flight curtesy staffing, Terminal staffing at ALL the same airports major carries have.

Yes, there would be such personal and equipment available for sale if a major carrier closed down, but the logistics involved in rehiring, retraining, reinsuring the small carriers is a huge nightmare that neither the little airline or the countless employees don't want to face.

The sheer scale of an operation like Delta is so huge that I don't think most people realize just how traumatic their just POOF disappearing would be. The FAA insures and clears in different capacities. Delta/United/Southwest etc.. the major airlines have different requirements and allowances for larger volumes of traffic, International, clearance/location of terminals and runways at different airports, etc... Re-checking, "upgrading" smaller airlines to be FAA approved for such a massive rise in traffic volume would be amazingly difficult and troublesome, not to mention dangerous if it were rushed to compensate for a multinational carrier disappearing.