On what is expected to be the busiest air travel day of the Thanksgiving holiday period this year, the Federal Aviation Administration is warning it may need to implement a ground stop or ground delay program at Newark Liberty International Airport.

Bad weather and not enough FAA employees caused more than 200 delayed flights Tuesday, according to United Airlines officials.

You’ve done everything by the book — got to the airport hours before departure, followed TSA guidelines about what can’t be put in carry bags, even remembered to wear slip-on shoes to make the getaway to the gate faster.

It is no secret the week of Thanksgiving is among the busiest for U.S. airports. The FAA said it is implementing measures to keep air traffic functioning, but such measures could delay flights.