The boosters were equipped with four large swept-wing fins at the extreme rear, behind the rocket exhaust, using a diamond cross-section suitable for supersonic lift.
Jet engines these days burn much less fuel at slightly slower speeds than the original designs that influenced the swept-wing designs of the '50s and '60s.
Both aircraft were turboprop airliners, with straight wings, which tend to be more susceptible to inflight ice accumulation, than are swept-wing jet airliners.
