Assuming they could get one there in time, no I wouldn't doubt it. Not sure how deliberately murdering hostages is constitutional but then neither is most of what the government is doing.
How many jets patrol the US mainland now? What is their response time?
I am assuming the white house has AA, but what about congress?
If required, the murder of innocents strapped to or contained within a weapon of war is totally legal. It has been legal for hundreds of years.
I can't speak authoritatively, but jet response time to a breach of a sensitive no-fly zone is in the single-digit minute range. [0] I would be shocked if every major government facility wasn't surrounded by a no-fly bubble. I would be surprised if we didn't have the capability to send fighters to anywhere in the CONUS within ten minutes.
[0] Quite some time ago, I was living near Tacoma, WA when the POTUS was visiting. There was concern that an aircraft was going to enter the temporary no-fly zone around the POTUS, so a couple of jets from the nearby base were scrambled and cleared to go supersonic -maybe- 1,000 feet off the deck. The din and air pressure change was incredible; it was if a tremendously large bomb had gone off some distance away.
Do you honestly believe that Air Force hardware won't be used to destroy a hijacked passenger jet that appears to be in service as a weapon? I don't.