Wizz is Europe's third-largest budget airline behind Ryanair and easyJet.Joan Valls/Urbanandsport/NurPhoto via Getty ImagesPeople are booking summer vacations later due to uncertainty from the Iran war."What we see is the trend is 'wait and see,'" an exec from airline Wizz Air told Business Insider.The budget carrier's CEO also said he doesn't expect widely feared jet fuel shortages to hit Europe.Travelers are holding back and booking summer vac…