And the fighter units at Andrews AFB were doing exactly what that day when the 757 went into the Pentagon?

On 9/11, Langley AFB and Otis AFB actually had the alert duties in the region. That means the had one pair of fighters ready, probably at Alert 15 or thereabouts. (Otis got its birds off in 10 minutes from the scramble order). The Langley fighters were sent to higher alert (probably Alert+5) at about 0909, as a possible backup to the Otis birds en route to New York. They didn’t actually get the launch order, now toward the DC area, until 0924 and got airborne at 0930. They were 150 miles out when American 77 hit the Pentagon at 0938.

The two fighter units at Andrews AFB (one DC Air National Guard F-16 squadron and one Marine Corps Reserve F/A-18 squadron) didn’t have an alert assignment and so had no aircraft standing by to launch on short notice. The DC ANG put its first planes up at 1038, about an hour after the Pentagon was hit. That’s actually pretty damn fast to get planes armed and airborne from a dead stop. To manage it that fast, someone probably broke some rules to get live weapons out of storage before they were given legal orders to do so.

The timing of this is all in the official 9/11 commission report.

There was a very real problem – but the whole reason that people were up in arms about the selection of the Super Etendard was that the problem was one which arose when the Jaguar had lost an engine. As a single-engined aircraft, the Super Etendard’s capabilities with an engine out were even less impressive.

Yeah, but assuming that both engines are equally reliable, a twin-engine aircraft actually has higher odds of suffering an engine failure on any given sortie than a single-engine aircraft. If it can’t land safely on one engine, the twin is actually going to suffer higher losses due to engine failure.