land goon or stop the m3 far enough away so troops have to run for a bit.
after they are all out, do /.ef, then go to hanger, and hop into an attack plane, in attack mode.
then get on the runway in the plane, before troops capture the field.
then you have a capture in attack mode.
oh if memory serves me, it doesn't stay on your personal score.
it does stay on squad score. IIRC, been awhile since done it. well was in AH1 when I did it. not sure how it works now.