Complex sentence: First, the vast increases in speed these jet aircraft in recent history only recently have permitted in terms of mass transit tourism to reach remote culturally diverse areas of the world which would not have ordinairaly been possible on the average persons available free time.
Split into simpler sentences: First, the vast increases in speed these jet aircraft in recent history only recently have permitted in terms of mass transit tourism to reach remote culturally diverse areas of the world. These area would not have ordinarily been possible on the average persons available free time.