F-1 students who travel outside of the United States during a cap-gap extension will not be able to return to the United States in F-1 status. They must be prepared to apply for an H-1B visa at a U.S. embassy or consulate abroad.
Travel Tip: An H-1B professional may enter the United States up to 10 days prior to his/her H-1B start date, i.e. September 20 for an October 1 start date. Therefore, if an F-1 student wants to travel over summer, it is best to plan to travel in September, apply for an H-1B visa at a U.S. embassy or consulate, and return to the United States on or after September 20th. However, s/he cannot start H-1B employment until October 1, the first day of the H-1B.