The FDNY reduced staffing by one firefighter for 60 of its engine companies today.
The move leaves all of the city's 194 engines staffed with four firefighters and one officer.
No firefighters will be laid off as a result of the move and it will save the city an estimated $30 million in overtime, according to a press release.
The FDNYs 15-year agreement with the Uniformed Firefighters Association expired at midnight last night, allowing the city to make the change.
"We just recorded the fewest fire deaths on record and our response time to fires is the fastest ever," Fire Commissioner Salvatore J. Cassano said in a statement. "Our number one commitment to this city has always been and continues to be the safety of New Yorkers."
The FDNY proposed the staffing reduction in last year's budget and gave notice to the union that it would not be continuing the 'Roster Staffing' agreement, which provided for the fifth firefighter on 60 engines.
The city's 143 ladder companies will continue to be staffed with five firefighters and an officer.
No other fire department in the country operates with five firefighters on an engine, according to the FDNY.
The Uniformed Firefighters Association and the Uniformed Fire Officers Association both filed an action with the Office of Collective Bargaining seeking to keep staffing at the current level, according to media reports.