Please read
(a) pages 7 through top of page 9 for first three topivs: Armstrong Line, birds, and clouds;
(b) page 13 for fighter aircraft (F-35);
(c) page 15: helicopter: "It can fly backwards or sideways and turn in the air in ways airplanes cannot. * * * Helicopters can fly as high as 25,000 feet (7.6 kilometers), although they cannot hover [without moving anywhere] above about 11,000 feet (3.4 kilometers) without the help of air currents. Above these heights, the air becomes too thin to create the needed lift."