Transfer between Heathrow and Gastwick

You should be OK. You probably will get through customs quicker and it is an hour bus transfer plus some waiting time between the two.

Four hours is the MINIMUM I'd allow for this transfer. (Five would be better.) If you arrive at Heathrow on time, get through immigration in a timely manner, and aren't caought in extra heavy traffic on the M25, you'll make it. There is frequent direct coach service between Heathrow and Gatwick. See www.natioalexpress.com for timetables and fares.

Thanks for your responses. I feel better since I've got 4 hours 4 minutes and I'm on a Sunday. I would HOPE the traffic is a little easier at 10 AM on Sunday.

I checked the Gatwick airport site and they suggest being there 3 hours before your flight.

So crazy. Hard to believe it takes that much time to get from airport to airport. I've thought about changing my flight from Rome from Sunday to Saturday afternoon and enjoying some of London at night and early morning before heading to the airport.

Traffic shouldn't be an issue on a Sunday morning. However, a late arrival, a delay in getting through immigration, or a longer than usual wait to claim your luggage could happen any day of the week. And then there is the recommended three hour check-in for flights to the US. (I assume that you'll be on your way home.) Flying out of Rome on Saturday and spending a relaxing evening and morning in London sounds like a good idea to me. Far less nerve-wracking than wondering if you're going to make your connection.

We flew home from Rome, too, but we went through Chicago and then to DFW. I don't know if there is service from Chicago to Tulsa, but I'd look at that rather than fooling with Heathrow and Gatwick.