Glenn boarded the Friendship 7 spacecraft at 11:03 UTC on February 20, 1962 following an hour-and-a-half delay to replace a faulty component in the Atlas's guidance system.
The hatch was bolted in place at 12:10 UTC.
Most of the 70 hatch bolts had been secured, when one was discovered to be broken.
This caused a 42-minute delay while all the bolts were removed, the defective bolt was replaced and the hatch was re-bolted in place.
 The count was resumed at 11:25 UTC.
The gantry was rolled back at 13:20 UTC.
 At 13:58 UTC the count was held for 25 minutes while a liquid oxygen propellant valve was repaired.

At 14:47 UTC, after two hours and 17 minutes of holds and three hours and 44 minutes after Glenn entered Friendship 7, engineer T. J. O'Malley pressed the button in the blockhouse launching the spacecraft.
O'Malley said, "the good Lord ride all the way," and then capsule communicator Scott Carpenter uttered the famous phrase "Godspeed, John Glenn."
Due to a glitch in Glenn's radio, he did not hear the Carpenter phrase during launch.
At liftoff Glenn's pulse rate climbed to 110 beats per minute.

30 seconds after liftoff the General Electric-Burroughs designed guidance system locked onto a radio transponder in the booster to guide the vehicle to orbit.
As the Atlas and Friendship 7 passed through max Q Glenn reported, "It's a little bumpy about here."
After max Q the flight smoothed out.
At two minutes and 14 seconds after launch, the booster engines cut off and dropped away.
Then at two minutes and twenty-four seconds, the escape tower was jettisoned, right on schedule.

After the tower was jettisoned, the Atlas and spacecraft pitched over still further, giving Glenn his first view of the horizon.
He described the view as "a beautiful sight, looking eastward across the Atlantic".
Vibration increased as the last of the fuel supply was used up.
Booster performance had been nearly flawless through the entire powered flight.
At sustainer engine cut-off it was found that the Atlas had accelerated the capsule to a speed only 7 ft/s (2 m/s) below nominal.
At 14:52 UTC, Friendship 7 was in orbit.
Glenn received word that the Atlas had boosted the MA-6 into a trajectory that would stay up for at least seven orbits.
Meanwhile, computers at the Goddard Space Flight Center in Maryland indicated that the MA-6 orbital parameters appeared good enough for almost 100 orbits.
Glenn boarded the Friendship 7 spacecraft at 11:03 UTC on February 20, 1962 following an hour-and-a-half delay to replace a faulty component in the Atlas's guidance system. The hatch was bolted in place at 12:10 UTC. Most of the 70 hatch bolts had been secured, when one was discovered to be broken. This caused a 42-minute delay while all the bolts were removed, the defective bolt was replaced and the hatch was re-bolted in place.  The count was resumed at 11:25 UTC. The gantry was rolled back at 13:20 UTC.  At 13:58 UTC the count was held for 25 minutes while a liquid oxygen propellant valve was repaired.
At 14:47 UTC, after two hours and 17 minutes of holds and three hours and 44 minutes after Glenn entered Friendship 7, engineer T. J. O'Malley pressed the button in the blockhouse launching the spacecraft. O'Malley said, "the good Lord ride all the way," and then capsule communicator Scott Carpenter uttered the famous phrase "Godspeed, John Glenn." Due to a glitch in Glenn's radio, he did not hear the Carpenter phrase during launch. At liftoff Glenn's pulse rate climbed to 110 beats per minute.
30 seconds after liftoff the General Electric-Burroughs designed guidance system locked onto a radio transponder in the booster to guide the vehicle to orbit. As the Atlas and Friendship 7 passed through max Q Glenn reported, "It's a little bumpy about here." After max Q the flight smoothed out. At two minutes and 14 seconds after launch, the booster engines cut off and dropped away. Then at two minutes and twenty-four seconds, the escape tower was jettisoned, right on schedule.
After the tower was jettisoned, the Atlas and spacecraft pitched over still further, giving Glenn his first view of the horizon. He described the view as "a beautiful sight, looking eastward across the Atlantic". Vibration increased as the last of the fuel supply was used up. Booster performance had been nearly flawless through the entire powered flight. At sustainer engine cut-off it was found that the Atlas had accelerated the capsule to a speed only 7 ft/s (2 m/s) below nominal. At 14:52 UTC, Friendship 7 was in orbit. Glenn received word that the Atlas had boosted the MA-6 into a trajectory that would stay up for at least seven orbits. Meanwhile, computers at the Goddard Space Flight Center in Maryland indicated that the MA-6 orbital parameters appeared good enough for almost 100 orbits.
Mercury-Atlas 6