Both are definitely older than their peers of the day, although Comet appeared first in 1939's Pep Comics #1, when he sported an entirely different. He was scientist John Dickering, an obsessive compulsive chemist who injected himself with "lighter than air" gases that gave him "leaping" abilities (read: flight) and vicious optical blasts curbed only by the glass visors he had to wear to avoid shooting them indiscriminately.
Christopher Smith also dappled in the sciences, more engineering than chemistry yet with similar results. A career diplomat, he obsessed with the fragile state of world peace or lack thereof, and hence fashioned a costumed in 1966's Fightin' 5 #40, including a jet-pack for flight and a helmet that included a destructive laser from the eye piece. Great minds think alike, it would seem.
Never fear, for after a quick bout with comic book death in the 40's, Comet was revived by an alien princess (who then herself bit the proverbial dust) and Johnny returned as an alien diplomat... resuming his interest in Earthly affairs of state. Christopher himself stepped outside his United Nations' sanctioned role to zap warlords and alien shape changers living under the Earth who stymied the peace process. And meanwhile, both ended up teaming up with a pair of buggy buddies we discussed previously, to fight against evil.