It truly depends on what type of aircraft you are referring to. There are modern Experimental aircraft such as the X-type aircraft. The fastest of those, the X-43, has achieved speeds in excess of Mach 7.
Then there are modern fighters, such as the F-35, F-18E/F, F-16, etc... The fastest of these can reach around Mach 2.
Modern airliners such as the 737, 747, 757, etc. cruise at about Mach .9 ...
And modern, General Aviation, single engine aircraft like Cessnas, Pipers might reach speeds of up to 150 MPH.
planes are so big now so they can carry more people and more fuel so they can go farther carrying more people.
depends on the plane.
because planes are fast and they can go to place that boats, cars, ect. can not. and for quicker transportation
over 14 mph
no not at all they are very slow, slower than snails
If you compare the planes of World War 2 they will seem very slow next to Jets. However, if you compared the planes of World War 2 to the planes of World War 1 and they were very fast and modern. So when you ask why they are slow it depends on those factors. They seem slow today because they did not have jet engines. However, they could go 250-450 miles an hour and that was fast then. Some of those very same planes race against one another in races around the United States. The race planes can go 350-400 miles an hour on average.
1 metre per hour
Some rocket planes can go as fast as six times the speed of sound. Most military fighter planes do not go faster than twice the speed of sound, and the typical civilian passenger/transport plane goes slower than the sound barrier.
Compared to today they were very slow. Many could not go much faster than 100 mph. Most modern cars are capable of greater speeds than these 'planes.
planes are used for cargo shipping, passenger shipping, or just sight seeing.
yes
About 300mph. They are not the fastest cars though - unlike with planes, jet cars are faster.