They can fly into Amman or Aqaba and take a sweaty bus ride to the Allenby Bridge. Whether Israel lets them in depends on whether Abbas-Hamas and the PLO have been on best behavior the week before. Don't like that? Need to recognize Jewish Israel and negotiate a peace agreement, not run to the IUN for a "state". A PLO airport? - fat chance, not after the Gaza airport was used to smuggle weapons. Besides, getting to it means overflight rights over Israeli airspace, which sovereign Israel is free to veto (answer: see "negotiated peace" above).