I come back shortly after I expect the aircraft to arrive and find that I have three! Darn it...I missed some revenue and I now see my airport mate has occupied some of the routes I planned.
But, as I reported earlier, the Aircraft on Order did not show any other than the last one, though I admit not looking at My Aircraft page - maybe they were immediate delivery? However, this was after the initial 24 hours was past, when I placed those first two used aircraft orders. AND, I had already placed an order for new aircraft on that first day.
So, if I have not purchased any used aircraft, my airline still has that flag for new game entrants that allows for immediate delivery it seems. Best explanation I can think of.