S&P points out that the airline provided just 3.8% of Gatwick's total passenger numbers.
It says: "Given the timings of the slots, we expect they will be attractive to other airlines. If the slots used by Thomas Cook are resold swiftly, the net loss of passenger numbers could be less than 1% of the total in the financial year to March 31, 2020."
The ratings agency adds: "It has taken about two years for Gatwick to substantially recover the volumes lost after the collapse of Monarch Airlines in 2017. However, we expect passenger numbers to recover more rapidly this time because, owing to a legal precedent, the Thomas Cook receiver is likely to be able to market the slots more quickly.
"If the sale is completed within a relatively short time after the receiver obtains confirmation of Thomas Cook's right to these slots from Airport Coordination Ltd. (ACL), this would give airlines sufficient time to mobilize, market, and sell the seats for the 2020 summer season.
"The ACL will return to the pool any slots to which Thomas Cook does not retain the historical rights as of the end of October 2019, and they will be re-allocated.
"The EU slot-allocation rules give priority to airlines that are considered to use the slots most frequently and efficiently; that is, maximising the number of passengers per slot.
"Thomas Cook operated 16 pairs of slots per day, and while some will be sold by the receiver, any remainder will be offered via the pool. As a result, Gatwick could potentially benefit from the increased participation of airlines that offer regular services; fly long haul; and use larger, rather than smaller aircraft.
"Therefore, in the medium term, it is likely that after a short drop in passenger numbers, the demise of Thomas Cook may result in an increase in passengers flying via Gatwick."