What was the main reason why propulsion formed a hurdle initially in the quest to be able to fly? Around the year 1900:

Question

Engines supplying the required power were too heavy

Engines were incapable of supplying the huge power required to fly

Engines were too big

Engines were too unreliable

Answer 1

The main reason why propulsion formed a hurdle in the quest to be able to fly around the year 1900 was that engines supplying the required power were too heavy. At that time, the weight-to-power ratio of available engines was not sufficient to allow for powered flight, as a lightweight engine capable of providing enough thrust was crucial for sustaining flight.