Outward flights from Europe to the USA and Canada are almost always daytime flights. Since North American time is behind European time, this makes for a long day.
Return flights from the USA and Canada to Europe are almost always night flights, and while it is sometimes possible to get some sleep on the plane you will inevitably feel extremely jetlagged when you land back in the UK. Because of the time difference, the night will be greatly shortened, so as to almost create two continuous days without a proper sleep.
In order to get more rest, and generally to avoid complications, direct flights are recommended, although a change at this end (for example, in Amsterdam) is not so much of a problem as a change in the USA or Canada. Beware of charter flights which make refuelling stops in Bangor (Maine), etc.
On both the outward and return flights, as soon as you board the plane and settle in your seat make a point of resetting your watch to the time at the destination and try as far as possible to think yourself into the new time.
Try to get as much rest as possible on the flight. While actual sleep is unlikely, a doze with your eyes shut will help considerably. The sound quality on the in-flight "entertainment" headphones is so poor as to most likely induce a headache, especially as it is coupled with the drone of the engines.
Drink as much soft drink as possible, to avoid dehydration caused by the plane's air conditioning. Avoid alcohol, which increases dehydration.
On landing in North America, try to stay up to within an hour or so of your normal bedtime if possible, otherwise you will wake up very early in the morning for the first few days of the holiday. In other words, if you normally retire at 10pm, try to stay up to at least 9pm North American time. Achieving this objective will be difficult, but worthwhile. The jetlag effect is far less on the outward flight and apart from waking up early you are unlikely to suffer any other effects.
On returning to Eurpe, head for bed as quickly as possible and stay
there until late the following morning. The jetlag effect is very much
worse on the return flight, and will be sufficiently extreme to make driving
any distance potentially dangerous. You will feel tired and disoriented
for a few days, with the effect gradually reducing. A few early nights
will help speed recovery.
Remember to leave room for items purchased while on holiday, plus literature and momentoes such as motel directories, tourist booklets and leaflets, National Parks maps and other information, etc.
As well as the large suitcases which go in the hold ("checked baggage") each passenger can carry on one bag, provided it will fit in the overhead lockers or under the seat in front of you, both of which are fairly capacious. Ladies can take a handbag in addition to another bag.
Put all your essential documents in a carry-on bag. It's a good idea to include road maps and directions for the first night accommodation as well, in case you and your checked suitcases don't meet up at the other end.
Remember that for security reasons you must put any electrical, electronic and metallic items in carry-on bags, never in checked suitcases.
Before you fly make a note of the three letter code for your destination airport and then when you check in make sure that code is put on each item of your checked baggage. You especially need to check this if you are using a "feeder" flight from a regional airport, where the person who checks you in is likely to be less familiar with your final destination's airport code.
You won't go hungry on the flight!
In order to combat dehydration caused by the plane's air conditioning, drink as much soft drink as possible during the flight and avoid alcohol.
If for medical, religious or ethical reasons you have any special requirements regarding meals on the plane then let the airline know well in advance and they will make arrangements for you to receive an appropriate special meal.
While most of the time you will hardly know you're moving, you may encounter some turbulence for brief periods. For this reason it's a very good idea to keep your seat belt buckled up, though perhaps only loosely, throughout the flight.