TWO PLANES fly high over the two escalators at the Air and Space Museum. These babies were among the many brainchildren of Ed Heinemann and Clarence (Kelly) Johnson, revolutionary aircraft designers who are being honored in a small exhibit, "Designers for the Jet Age," in the museum's Pioneers of Flight gallery.

The one up there with the sky-blue belly, that's the Lockheed F-104 Starfighter, designed by Johnson in the mid-'50s. The first fighter plane in the world capable of operating at Mach 2 (twice the speed of sound), it was a far cry from the "Merlin I Battle Plane" -- the first plane Johnson ever dreamed up, at age 13.

The white needle-nosed plane hanging over the other escalator sports a yellow band on its tail with the initials "NACA," for National Advisory Committee for Aeronautics. This Douglas 558-2 Skyrocket ws the right stuff for flyboy A. Scott Crossfield, who became the first pilot to hit Mach 2 when he jockeyed one just like it on November 20, 1953.

Heinemann designed this rocket-propelled machine, probably using the same T-square, compass and triangle that are displayed here. Computers having replaced them in the aeronautics business, these crude tools look like Stone-Age relics. And the doodles of planes and cartoon characters that Heinemann scratched on his plastic triangle are hieroglyphics.

DESIGNERS FOR THE JET AGE -- At the Air & Space Museum through April 1986.