can a plane fly vertically if so for how long is it possible for it to fly that way. and what is it called when the plane tilts vertically to go downward.
I am assuming that by vertically you mean with the nose pointed straight up, not with the wings pointed up and down.
A plane can fly vertically as long as the thrust from the engines is sufficient to overcome the weight of the plane plus air resistance. Most commercial aircraft do not generate enough thrust to let them climb vertically but some military aircraft do. They can climb vertically as long as the engine can get enough oxygen from the air to burn enough fuel to produce the thrust.
When a plane tilts vertically to go downward it’s usually called a dive.
In almost any airplane you can build up enough momentum to climb vertically for short time. To sustain that climb, you would need more thrust than weight. Not very many can.
An F-15 Eagle can accellerate while going straight up. When an engine has been out of the airframe that the first flight afterwards they will have the pilot come off the runway and pull straight up and go into afterburner and climb that way to 50,000 feet. This is called an Eagle departure.
I used to have an office just off the end of the runway at Portland International Airport. When one of the Air National Guard F-15s did an Eagle departure, the concrete walls in my building would shake.
Amazing thing to watch and hear.
If the plane tilts down and goes down more or less straight it’s called a “dive”.
If it turns round and round on its length while doing a “dive” it’s called a “spin”.
If either of the above continues until the plane meets the ground, it is called a “crash”.