Aircraft full of passengers landing at the same time as emergency vehicles trying to get to an incident of potentially unknown severity seems like a recipe for disaster.

Aviation is a shining example of how thought about risk, learning from failures/mistakes and evolving standard operating procedures can almost completely de-risk an inherently risky environment.

I came across this article after the incident in SFO earlier in the week:

http://en.wikipedia.org/wiki/Boeing_777

No flight related deaths since it began service in 1995 - I've been thinking about that all week. That is some inspirational engineering.

A Heathrow spokesman said: "Arrivals and departures were temporarily suspended while airport fire crews attended to this incident."

"This is a standard procedure if fire crews are occupied with an incident."

They only have the ability to deal with one emergency at a time? That strikes me as sub-optimal, especially if the "emergency" is contained within a single parked aircraft. Diversion is probably costing all the airlines involved a ton. I think it would be worthwhile for emergency facilities to have a backup.

Anyway, I suspect the real reason is that an emergency is a dynamic situation, and an airport is a large complex barely-controlled environment. Sure, probably parts of the airport could stay in use, but it would take a lot of coordination and analysis to do so safely, and there's really no time to do that. So you just shut it down.

You know what's going on now, so it's easy to say; but if you're running the airport and all you know is "aircraft on fire", what do you do?

As for the cost, yes, but airlines are fairly risk adverse creatures and I'd imagine they'd have adequate insurance to cover such eventualities.

The runways and taxiways that planes would normally be using arriving and departing are being used, or may need to be used, without delay by emergency vehicles.

The simplest and safest way to assure that this can be done, and done safely, is to not have aircraft using them for landings, takeoffs, and taxiing.

Okay, that makes sense now: The regular infrastructure is needed for the emergency infrastructure. The analogy would be, that an admin could log in unless the site were taken down. That would be terrible for a website, but it makes sense for physical infrastructure.