The value of the pound dropped 12% after the Brexit vote on June 23, making flights across the pond cheaper than they’ve been in three years. While the move has been a boon for US travelers, US airlines are adjusting their flight schedules to stay profitable.

On Thursday, Delta Airlines (DAL) announced it would reduce the number of flights from the US to the UK by 6% on its winter schedule. The decision was made after the airline’s operating revenue for the June quarter dropped by $260 million,or 2%, $65 million of which was because of currency fluctuations.

The airline spent $408 million less on fuel expenses compared to last year, and those savings helped Delta’s earnings rise 4% to $1.5 billion in its second quarter. Still, the airline hopes to keep making money by tweaking its winter schedule.

“As we look to the remainder of the year, the large year-on-year savings driven by lower fuel are largely behind us and it is important to achieving our long-term financial targets that we get unit revenues back to a positive trajectory,” said Ed Bastian, Delta’s chief executive officer.

United Airlines (UAL) is also adjusting its flight schedule; it announced it’s reducing the number daily flights from Heathrow to Houston from three to two starting on Oct. 30. To accommodate travelers, the airline will begin using the Boeing 777-200, which holds more passengers than the current aircraft, for the two remaining daily trips.

On the flip side, United has decided to increase the frequency of flights on other routes, adding a second daily nonstop flight from Heathrow to San Francisco. Starting April 5, 2017, British Airways will also add a second daily flight from Heathrow to Los Angeles.

Airlines might be shuffling flights around, but US travelers have never been more interested in visiting the United Kingdom. After the Brexit vote, Hopper, an airfare booking site, reported that searches for flights from the US to London and Edinburgh, Scotland, spiked by more than 50%, peaking on July 1. Around the same time, airlines reduced prices by 10% to 15% on flights from the US to destinations in Britain.

Airfare to Europe is currently lower than in past years, but it’s still a tad pricey because we’re in summer peak season. For example, right now a seven-day round-trip flight from New York to Heathrow on British Airways will cost about $1,258.

According to FareCompare, an airfare search engine, the best time to book a trip to London is on Aug. 23, when fares are expected to drop as airlines begin their fall season. If you wait until then, that same British Airways flight will cost around $746 if you travel in September and $725 if you wait until October.

In other words, you’ll save big money if you wait until the summer winds down to book your trip to the UK.

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