Thomson Airways says it's activating contingency plans to switch customers to other aircraft, in the absence of a delivery schedule from Dreamliner manufacturers, Boeing.
The holiday firm is contacting those affected to tell them they will be travelling on Thomson Airways 767 long haul aircraft.
The supplement paid for the 787 Dreamliner flight will be refunded to those customers who proceed with their original holiday bookings, and customers will also have the option to amend their holiday without incurring any amendment fees."
– Thomson Airways statement
They added: "We understand how frustrating and disappointing this news will be for those customers looking forward to flying on the 787 Dreamliner, we are equally as disappointed that Boeing was not able to confirm a delivery date for us. Unfortunately these circumstances are out of our control."
Gatwick Airport has recorded a fall in passenger numbers with 0.8% less people choosing to fly in January compared to last year.
The airport said "economic conditions remain challenging" and the weather was also affecting its operations.
However, it continued to see growth in domestic and long haul markets with 6,800 and 21,900 more passengers, respectively.
Nick Dunn, chief financial officer, said: “In January we saw a slight decline in the number of passengers travelling through Gatwick, which is a reflection of lower European traffic. However this was balanced with growth from long haul airlines serving Asia.
“We are delighted that Garuda Indonesia has chosen Gatwick to operate a vital new direct route to a key high-growth business market.
"Jakarta is also a major hub airport for South East Asia, giving UK passengers even more access and choice to the region.”
The UK launch of the Dreamliner, the so-called plastic plane of the future, is set to be delayed because of continued fears over safety.
Thomson was due to fly its first Boeing 787 from Gatwick in May but delivery of its planes is now on hold.
The first should have arrived in the next two weeks. The airline is the UK launch customer. All 50 of the planes in service have been grounded since a battery fire on a Japanese Airlines flight in Boston last month.
Safety officials in the USA ordered all the Dreamliners to be grounded following safety tests. They will not fly passengers until a solution is found to the problem.
A test flight took place over the weekend but the issue remains unresolved. Experts say a solution could be months away.
The Dreamliner was developed at Farnborough and many components are built in the region supporting thousands of jobs.
Airlines have placed orders for more than 800 of the planes. Made from a composite of plastic and carbon they burn less fuel.
Inside windows are twice as big and the planes have more space. A new air system is aimed at reducing jet lag. Thomson has launched an advertising campaign calling the 787 the "future of long-haul travel".