Basic question about layovers

I am flying from the US to Tanzania via Heathrow on several airlines. I have a layover in london of about 7-8 hours. I want to meet up with family and make a quick trip to Windsor during this layover.

Can I check my bags through from the US? Or do I only use the US-LHR part of my ticket, collect my bags. And then check in again in LHR with the TZ section of my ticket?

Thanks
emm

If the two airlines (i.e. the one you're flying to LHR, and the one you're flying out of LHR) have an interline baggage agreement - and most major airlines do have them - then your luggage can be checked through.

However, unless the two airlines are close partners and have specific agreements - meaning the first airline issuing boarding pass for the 2nd leg - then you'll need to check-in at LHR again.

Depending on whether your 2nd airline has a check-in or ticket desk open when you arrive at LHR, you may have to check-in only 2-3 hours prior to the flight, and not right after your arrival to LHR. That means your 7-8 hours is now 5-6.

BA - and possibly some other airlines - can get difficult about through-checking via LHR if the different sectors are on different tickets, even though just about every connection at LHR is, as rkkewan says, covered by interline agreements.

However, many North American checkin agents are spectacularly ignorant about the mechanics of international travel - but are refreshingly aware of their ignorance. So looking them straight in the eye and telling them, if they hesitate to through-check, that you've done it before and it's OK, always seems to work. And however prissy some airlines are about that in theory, in practice the system at LHR always processes bags marked for transfer.

The ridiculous system many airlines at LHR have of opening checkin only a few hours before departure can seriously mess up transfers like yours. But, if you've checked your bags through already, there's probably no need to check in more than 60-90 minutes before departure anyway, even to longhaul destination tike Tanzania. And most airlines - especially BA - at times they won't allow physical checkin bizarrely allow phone or online checkin , which you can do either before you leave home or from a phone box or internet terminal at LHR. Some airlines require pre-registration for online or phone checkin, and you should do this before your journey starts.

However determined many airlines are to make life as difficult for passengers as possible, there's usually a way of imposing common sense on them.

Thanks for the info. I was unsure - with all the various security issues - whether this was still allowed. The two airlines are American and BA - so my guess is they'll have an agreement.

Thanks
Emm

Yes if it's AA and BA you'll be fine.