I just can't believe that. We're now in a tarmac delay due to weather (thunderstorms in MIA have caused the ramp to close), after which point the pilot has said catering still needs to service the plane before we can depart. Airlines are required to provide working lavatories during tarmac delays, I find it hard to believe the FAA would certify a plane that is physically incapable of providing a working lavatory on the ground.