Can passenger planes carry cars in the baggage deck?

I can speak confidently but not authoritatively on this, so let's consider this answer tentative. I would be glad to be corrected.

Military gliders were replaced by helicopters after World War II, and no one seems to have found a civilian use for large ones. Unpowered flight is a sport, now, so there don't seem to be any with more than 2 seats. The only recent exception I can think of is the Space Shuttle, which was unpowered during its return from orbit.

Usually it is airspeed of the aircraft. Each aircraft has different airspeed requirements for operation the flaps or landing gear. Usually that speed is determined by the airframe manufacturers and the design of the flap system component. You could built it strong enough to handle any airspeed, but a plane can only carry so much weight. If you built everything to work without any limitations you might have an airplane too heavy to fly. Designing a plane is a balance between lifting capability and weight. Both of these are important design parameters.

Yes. There are propeller driven airliners in service today, mostly on short routes.

The safest time to fly is after such an incident because all pilots are double checking themselves to make sure it doesn't happen to them.

In the U. S., the last fatal jet airline crash was in 2009. Here's a reference.


https://www.reuters.com/article/us-aviation-safety/2017-safest-year-on-record-for-commercial-passenger-air-travel-groups-idUSKBN1EQ17L

How much fuel would that be in pounds? Remember that the plane will need to get into the air, if it is too heavy it wont be able to takeoff. Also what if something happens that requires the plane to come back and land?

Aircraft too heavy. Weight is extremely valuable/expensive and the weight of a parachute system would be too heavy and costly, sacrificing room for paying passengers.

As the wings are lifted by differences in air pressure and gravity acts on the fuselage, the extra fuel load in the wings won't really affect the curvature. Rather, this is for the large storage capacity (volume) of the wings, and the safer option that your fuel tanks are outboard, rather than crew / passengers sitting directly on top of a "belly" tank. In event of a fuel-fire or crash, there is still a chance of fire being extinguished, or fuel-laden wings breaking away in a major crash. The spread-out mass of the wings also adds to stability by increasing the inertia.