Aerofiles. It provides basic specs for virtually every aircraft type ever built in the United States. Even better for us Wikipedians, it appears to meet even the strict criteria of a reliable source since some of its major contributors are published authors in aerospace history. Google also showed up a preserved Standard E-1 at the Fantasy of Flight museum, and their website had another important spec (gross weight) and a bit more history. I've updated the E-1 article accordingly; you might want to do the same for some of the other recent articles you've created.
- British aircraft
- Russian and Soviet aircraft
- French aircraft
- Italian aircraft (needs a little Italian to navigate - hover your mouse over the links marked "Schede" to the left of the screen)