of the airports in the uk are closed. >> correct. this is not precautionprecautio. this is a mandatory do-not-fly zone literally, because this is a particle blonwn up many thousands of times. you don't want that going through your car's engine, let alone a jet engine, and this because it's ash melts back down into lava and then like glass, like you said earlier, like ob siddian, and then it deposits itself on the back of the jet and the jet engine on the plane can choke itself. >> yep. >> look what happens here. you hit the particles, i know they're small, but you hit them with the plane, it scours the plane, you can't even see out of the windows at all and it can also just scour all the paint off and actually put dents in it if it hits it hard enough. so, you can -- there are literally there are mandatory reasons why you don't fly in volcanic ash. >> right. >> and this is the time. >> we'll stay on that. we'll be back with you in a minute. there have been instances where planes have had all of their engines shut down because of it.