Can I get off a plane if we landed on Shabbat?
Yes but you cannot leave the terminal till after Shabbos
Is this only bediavad for people whose flights were delayed? Would it ever be permissible to knowing fly before Shabbat starts knowing that you will land after sundown?
It would not be permitted to knowingly fly before Shabbat or Yom Tov starts knowing that you will land after sundown.
Furthermore, one is required to begin his travels early enough that he or she is giving double the amount of expected time to arrive. Meaning, if your trip is an 8 hours trip then you would be required to leave a minimum of 16 hours before Shabbat or Yom Tov.
This includes driving or flying. So if you are travel from Lakewood to Brooklyn on a Summer Friday which can take about 2+ hours you would be required to leave with a minimum of 4+ hours before Shabbat.
I assumed that was the answer. I’ve met many people who fly on Friday towards Asia to go over the international date line and “beat” Shabbat.
Glad to know the halakha.