Unrestricted climb
A zoom climb is a climb where the rate of climb is greater than the maximum climb rate using only the thrust of the aircraft’s engines.
According to Wikipedia, typically referred to as an “unrestricted climb”, pilots will take off and accelerate to a high speed near the ground and then pull the aircraft vertically or nearly vertical to quickly climb to the aircraft’s cruising altitude.
Even though zoom climbs are somewhat commonly performed by modern fighter aircraft, airliners can perform unrestricted climbs too.
Boeing 757 unrestricted climb
Frank Fowells, former US Naval Aviator and former Boeing 757 pilot, recalls on Quora;
‘Ahhh… Now that can be fun!
‘I once had an early morning B757 ferry flight from BWI to PHL. A fifteen-minute flight for that plane. Just the captain, me, and 15,000 pounds of fuel on board. A very light fuel load. For takeoff we used the minimum permitted engine thrust allowed and were given permission from ATC for an “unrestricted climb to 10,000 feet”. With the big an airplane you are not slammed back in the seat for takeoff but with experience you certainly know when you accelerating quickly.
‘At lift off the captain kept pulling the nose up to keep the speed within limits and I was madly raising the landing gear and flaps. We were very quickly cleared for a 180° turn and completed the turn as we leveled off at 10,000 feet all in under two and a half minutes. I looked out the right window and realized we were over the control tower. The entire event was done while within the fence line of the airport. I asked the ATC controller how it had looked he said, “That was IMPRESSIVE!” It was a rush!’
Fowells concludes;
‘That is what pilots can do when there are no passengers on board.’
Photo by Tristan Thomas Own Work via Wikipedia