Originally Posted by
Raymoland
Sounds to me like a single pack issue. Packs are airconditioning units that keep the cabin pressurized. When one is inop it restricts aircraft to lower altitudes. At lower altitudes you get lower true airspeeds and if there were higher winds as well that could account for the slower speed.
I would buy this one except every other flight at similar times was between FL300 and FL340 and had at least 60 mph better ground speed. The original MX delay was for thrust reverser.