Trim is much more important in a large jet than it is in a Cessna because of the speed range it operates over. At lower speeds with flaps up, you need a high a

Trim is much more important in a large jet than it is in a Cessna because of the speed range it operates over. At lower speeds with flaps up, you need a high angle of attack to maintain altitude. This entails a very high stick load in a manual aircraft like a 737 unless you trim nose-up for it. With flaps down, you need much less angle of attack, so less nose-up trim. At higher speeds, flaps up, you need a low angle of attack, so trimmed much further down. At higher speeds still, you start to get mach tuck, and need to trim up a little. So that's quite a large range of angle of attack, and so trimming needs to be very effective. Now, at the same time, the airframe is not rated for aerobatics. So, you don't want to fit a huge elevator, because then it would be too easy to pull high-G maneouvers, and damage the airframe. It's all a compromise - very effective trim is a necessity in a large jet, and the elevator should be just large enough to give the control needed. The limitation then is that there may be parts of the flight envelope where the aircraft can be so far out of trim that the elevator struggles to overcome the trim. Normally well trained pilots would go nowhere near these parts of the flight envelope. This is why it's really not helpful when the automatics go awry, and put you there.