The plane had its landing gear retracted when it safely landed at about 1 a.m. Saturday.
All 34 people on board, 31 passengers and three crew members, walked away unharmed.
An airline spokesperson said the plane, which left Philadelphia shortly before 11 p.m. Friday, circled Newark in a holding pattern while working to get the landing gear down. After several failed attempts to get the gear down, the plane landed on its belly.
After landing, fire and rescue crews were standing by to foam the runway to make sure the turbo-prop plane didn't catch on fire.
US Airways and federal investigators are working to figure out why the landing gear got stuck.
The Associated Press contributed to this report.