In the FE model sustained space flight would be impossible due to simple physics. As they have said the object would need a constant source of acceleration to keep the earth from catching back up to it. However, that acceleration force would need to be greater than 9.8 m/s^2, which is the accepted force of UA on the earth. The reason for this is because if an object is being accelerated by another object (like us by the earth) as soon as that object becomes detached from the object(or force) which is acting upon it, its acceleration stops. This is how the FE model works, as it explains the phonomenom RE'ers know as gravity.
Herein lies a flaw in the FE model however. We all observe many objects flying around the earth everyday, birds, planes etc, all maintaining a relative distance to the ground. So then the lift generated by an airplanes (or bird) wings would have to be greater than 9.8m/s^2 in order to lift off of the ground and gain altitude. Now that is mildly believable, as air movement over a wing can exert a good amount of force. But then how is a baloon simply filled with helium able to float into the sky? This would imply that the baloon is able to exert an acceleration force exceeding 9.8m/s^2.