The airline blamed the cancelations on "operational reasons" but did not elaborate further, according to The Straits Times.
It apologized for the inconvenience caused to passengers and promised full refunds.
Some passengers expressed frustration.
"Just saying vaguely ‘operational reasons’ is disrespectful to your customers," a passenger wrote on social media.
Another wrote "Poor service."
On May 4 many parts of Singapore were flooded following torrential rains, affecting operations at Changi Airport.