Transatlantic travel with a 3 month old - any tips?

Hey guys, next week we're flying from Manchester (UK) to South Carolina via Chicago with Logan, our 3 month old. We're excited he'll get to meet his Mum's side of the family, but also a bit nervous about a long trip (19 hours door to door!). If you have any tips or anything that helped you on long flights or journeys please let me know. Cheers!