Bomber aircraft are air units which are armed primarily with bombs, and are meant to serve in air-to-ground roles. Generally,
Heavy bombers carry heavy payloads of bombs. They are not accurate, but can be called upon for heavy duty carpet bombing runs on enemy infrastructure. Heavy bombers are quite slow and carry more fuel, but are more vulnerable to anti-aircraft fire and fighters.
Light bombers are cheaper, but while they do not deal as much damage as heavy bombers, they have greater speed and accuracy as regards to their ordnance. Light bombers are useful for attacking enemy units, especially enemy heavy shipping, and like fighter aircraft can be used to spot hidden units.
The LOS of heavy bombers from  onwards increases with each level of Science undertaken. For all factions the default amont is +1,but German aircraft get a +3 LOS bonus, while British aircraft get an additional +1 LOS for every level of Science researched.
While not considered as normal aircraft, special attack aircraft are a genus of unit that is consumed upon instantly attacking. These can range from suicide attack aircraft as used by Japan, all the way to the terrifying V-1.