Five-time champion Roger Federer strolled into the US Open third round as fellow old-timer Lleyton Hewitt bid farewell in trademark fighting style.

On a dramatic day which saw a record created for the longest women's match, and a new Grand Slam high for retirements from the men's tournament, Andy Murray escaped his earliest exit in 10 years when he came back from two sets down to make the last 32.

There was also a late security scare when a drone crashed into the corner of Louis Armstrong Stadium.

Then, after midnight, 2009 and 2014 runner-up Caroline Wozniacki, the fourth seed, was knocked out by Czech world number 149 Petra Cetkovska who saved four match points to win 6-4, 5-7, 7-6 (7/1).

Cetkovska, who recently missed seven months of action with a hip injury, committed 60 unforced errors but unleashed 60 winners.