Addressing the London Assembly at City Hall during the Mayor's Question Time on Wednesday (October 19), Sadiq Khan said the wait is affecting the city's business prospects and gave his reasons for backing Gatwick.
Khan said: "The Government’s decision to yet again delay deciding where to build a new runway will cause unnecessary uncertainty for British businesses already struggling with Brexit.
"Now more than ever, businesses need certainty and stability in order to make investment decisions and to keep jobs in Britain.
"Instead they are getting dither and delay.
"Now it's time to get on with building a new runway at Gatwick, which can be built quicker, cheaper, and without the years of legal and political battles that Heathrow clearly faces."
A total of 29 cross party leaders - including London assembly members - have backed a letter sent by Khan to the Government, but he told members he is "yet to receive a response to the letter".
The Mayor didn't answer Assembly chairman Tony Arbour's question on whether he was willing to pledge money towards legal fees in order to challenge the decision should it be Heathrow Airport and insisted he will "review his position once a decision has been made".
A Cabinet decision on airport expansion is now believed to come on Tuesday (October 25).