What would happen to a flying aeroplane if there's suddenly a brick-size hailstorm?
There was a case where an easyJet Boeing flew through a hailstorm; the accident report is here, with a PDF download available, which lists some of the damage (which includes a cracked windscreen and damaged leading edges on wings and other surfaces).

There are photos showing the damage incurred, including the one below. Search for "easyJet hailstorm damage" to find more.