All our airplanes record out times based on the airplane actually moving. The -200's are more accurate because the are based on sensing the wheels actually rolling. The -900s, and I think the -700s are GPS based. I guess they updated a lot of the 900 software to make it more accurate but especially in the 700 you can complete the push and engine starts and still not have it trip the out time until you actually start taxiing. On some of the fleet we are allowed to ACARS dispatch with our actual out time if the computer didn't catch it correctly.