WASHINGTON—The Federal Aviation Administration has warned that 5G wireless operations can interfere with radio altimeters in Boeing 737s, impeding a crew’s ability to safely fly or land, but FAA officials stressed the issue poses little practical effect for airlines. Despite dire-sounding language in the FAA airworthiness directive issued on Wednesday about potential effects on 737 landings, it does not apply to aircraft flying into areas where the 5G environment has been rendered safe for aviation, which the FAA said includes nearly all airports. The overwhelming majority of commercial airports have either established 5G wireless buffer zones around them or lack 5G operations altogether, meaning that planes landing there are protected from radio interference warned about in the FAA directive, agency officials said on Wednesday. The FAA said the directive posted on Wednesday for most of Boeing’s 737 aircraft is very similar to notices issued previously for 737 MAX aircraft, as …