If they’re not the cheapest option, try searching by month to compare costs throughout the week.
When you fly from Doncaster to Philadelphia, you'll have zero airlines to choose from for your 5593 km journey. If you're planning to fly in peak season, make sure you book in advance to get a reasonable price. Or you could hold on and try to get a last-minute bargain.
If you're fairly flexible about when you want to fly to Philadelphia, searching by month will show you the cheapest times to go.
Once you've selected your flight, you'll need to fill out your details to book. And don’t forget to look at Netflights’ hotels and car hire – you could save even more money on your trip when you book everything in one go.