Answer by Thomas Zerbarini:
An aircraft's tubular fuselage acts as a Faraday Cage's as long as its a conductive material like metal. (Fiberglass and composites are not conductive materials)
Part of the FAA certification of a transport category aircraft (specifically Instrument Flight Rules Certified Aircraft) is that it demonstrates lightning protection
Title 14 of the Code of Federal Regulations (14 CFR) 23.1306, 25.1316, 27.1316, and 29.1316, Electrical and electronic system lightning protection
I have been struck by lighting many times in my career and I have never had an aircraft suffer any harm to any person or major component in the aircraft. The aircraft itself had sustained some damage (a few popped rivets, composite or fiberglass material burnt, some paint burning, etc..) Sometimes a radio or antenna would be affected or unusable if the antenna experienced the electrical current.