Covid-19 vaccines is entering its final stretch, parts of the travel industry are sprinting to a different finish line: airport testing.In hubs large and small, from JFK to Boston to Frankfurt, Germany, a variety of companies are figuring out how to scale preflight rapid and PCR Covid testing in hopes of facilitating safe air travel and lessening quarantine requirements for anyone who isn’t first in line for a shot.The leaders of that effort may come as a surprise.ALSO READ: Inside the race to save MollemIn the U.S., it’s XpressSpa, the purveyor of quickie mani-pedis and travel pillows.