That doesn't seem like a good argument for instituting a quarantine by blocking air travel but not ground travel. And why block everything including police, cargo and medivac flights for a quarantine?
Closing the El Paso airspace will reduce the number of people flying, but not stop it, lots of people will make the drive to Tucson or Albuquerque to catch a flight.
I could maybe see it if it was, say, LAX which is a major travel hub, but shutting down a small regional airport without also shutting down ground travel is "quarantine theater" rather than a real quarantine.
Tell me you've never been to west Texas.
...In Mexico, sure. The closest major US airport to El Paso is Albuquerque or Tucson, 4 hours each.