Welcome to FT!

These flights are on one ticket, correct? (Rather than two.)

1. Your bags will be tagged for LAS in London, but since New York is your first port of entry to the US, you'll need to collect them at JFK after immigration, and then immediately recheck them at the nearby counter. It's close-by, obvious, and simple.

2. You will need to go through passport control when you get off the aeroplane. There will be a second identity check when you go through security at the next terminal.

3. Connecting between the terminals is very simple. There is a little train connecting them.

4. Your timing should be fine. If you miss your connection, Delta will typically put you on the next flight.