Yes, there is a 24-hour Singapore Airlines cancellation policy, under which you can cancel a flight booking made with the airline within 24 hours from the time of reservation. No penalty will be charged if the cancellation is initiated within the specified time period.

How do I cancel my Singapore Airlines flight?

The different modes available to cancel with Singapore Airlines are described here for your reference:

Cancellation initiated with the team via the official website:

You can cancel with the airline through the online portal. The methodology that can be followed to initiate the cancellation process with Singapore Airlines is as follows:

Skim across the official page of Singapore Airlines.
Scan on the page to find the Manage Booking link.
Click on it and enter the credentials as being asked.
The booking page will be retrieved for you.
Scroll down to find the flight to cancel.
Click on the Cancel My Flight option from the menu list.
Proceed further, review, make payment and submit.
The team will share a confirmation email for the same.
Placing a call with Singapore Airlines for cancellation:

A direct call can be placed with the airline's team for the cancellation that needs to be made. You can call the airline team at +1(833) 727-0018, where the details of the cancellation that you need to make need to be specified. The agent would initiate the cancellation accordingly.

How much is the cancellation fee for a Singapore Airlines flight?

The average fee levied as part of the Singapore Airlines flight cancellation depends on the fare class, the destination chosen, and the total distance travelled. Thus, an average of 70 USD to 150 USD would be charged to you, which can vary.