best way...triple locking doors to the cockpit of converted bombers with functional Bomb bay doors. maybe auto open at 20,000?
I really don’t think you could get too many into a bomber’s bomb bay area. It would be best to just load them into a cargo plane, such as a C130. Once airborne just lower the rear loading ramp and point the aircraft’s nose upwards and they will all slide out.
I actually watched this happen to unwanted cargo in Vietnam.