Seeing this topic made me go and look for any backups I may have had. Unfortunately not. Other than being a bit time consuming, if you know the data required, you can get ready it brforehand. That's what I did. I got to the stage where I could add it into the aircraft.fsc without using the airplane edit from within.

63,MD11 Cargo another company,110000,410,290000,130000,50000,2500,290,2000,290,460,370,180,0, 3900
64,Transall,13128,300,49150,29000,20000,1250,180,1300,200,250,210,125,0, 999
65,Piper Cheyenne,1112,290,3946,2317,317,1000,125,1000,150,240,250,160,0, 1320

Entry # (increases by 1 for each additional entry)
Aircraft Name
Max Fuel
Cieling (FL)
Max Weight
Empty Weight
Load (payload)
Climb Rate (fpm)
Climb Speed
Descent Rate (fpm)
Descent Speed
Cruise Speed
Approach Speed
NOT SURE (but all aircraft have a zero there)
Max Range

All you would need to do is gather the data and write like the example, and you would be set. Doing them that way, my biggest mistake was the Entry #, they increase by 1 with each additional aircraft, and I would forget and repeat a number and that meant that it, and every aircraft that followed it in the list, were not seen by FSC. It was still easy.

Adding the aircraft in FSC is good, but I accidentally modified some of the default ones too often, so I switched my method of adding them to the one described above. It was safer for me.

Mark