Original sentence: Most commercial jetliners have a service (or certificated) ceiling of about 42,000 feet (12,801 m) and some business jets about 51,000 feet (15,545 m) while their absolute ceiling is much higher even if it isn't used for operational purposes because it is impossible to reach (because of the vertical speed asymptotically approaching to zero) without afterburners or other devices temporary increasing thrust and it isn't economically advantageous due to the low indicated airspeed which can be sustained
Edited sentence: Most commercial jetliners have a service (or certificated) ceiling of about 42,000 feet (12,800 m) and some business jets about 51,000 feet (15,545 m) while their absolute ceiling is much higher even if it isn't used for operational purposes because it is impossible to reach (because of the vertical speed asymptotically approaching to zero) without afterburners or other devices temporary increasing thrust and it isn't economically advantageous due to the low indicated airspeed which can be sustained