Did you drop a sarcasm tag? Anyone can make a fire on a plane as they allow lighters on a plane, and batteries, and any number of flammable objects. None of that is facing any scrutiny nor stopping crazy people from being crazy.
Yes it's possible to make a fire on a plane, but it would be even easier to cause a big fire if there was zero monitoring of bags. As flawed as airport security is, it should generally catch things like somebody trying to get a carry-on bag full of gasoline or extremely large lithium-ion batteries on board.
I take security that catches 50 or even 20% of threats any day over 0 security.
I've heard that cell phones often catch fire on planes, and the crews know how to deal with that. I guess they have to because the odds of one going up are pretty good across so many flights.
Flammable liquid and all high temperature lighters are forbidden, as are Li-ion batteries over 100kWh.
Ironically, both India and China forbid lighters on planes. Famously you see a collection of them around the bins just outside the airport as all the smokers leave them for others.