(CNN) Airline travel is bouncing back -- but so are American coronavirus cases. United Airlines presented sobering facts to employees Monday that bookings are tumbling as Covid cases soar. Also hurting travel demand: regulations in New York, New Jersey and Connecticut that mandate travelers from the pandemic's US hotspots quarantine themselves for 14 days. Near-term bookings at United's hub in Newark were only 16% of 2019 bookings as of July 1. But with the surge in Covid-19 cases and signs of a drop in bookings, airlines that added flights may have gotten ahead of themselves.