"The F84 ThunderJet often ran out of runway in the hot Korean weather and was known as the ""Groundhog"" because of this reluctance to become airborne. I noticed fairly quickly in MiG Alley that on take-off it is important to keep the flaps down until the speed has built up and to keep the climb out fairly shallow.
Other fliers have reported that a ""flaps up"" setting is best for takeoff, with a very shallow climb out... barely clearing the treetops at about 2 degrees climb angle."