It would take approximately 45 hours to fly around the world in a commercial flight plane.

Let’s understand how we calculated this flying time. Before calculation, we made few assumptions such as
- We are assuming that the plane will fly over the equatorial circumference of Earth which is about 24,901 miles (40,075 km).
- We have taken Boeing 787 also known as Dreamliner for the calculations.
- The average speed of a Boeing 787 commercial plane is considered as 561 mph (903 km/h).
- The airplane has sufficient fuel tanks to cover the circumference of the earth which means the airplane does not have to stop to refuel.
Based on above assumptions,
The time taken by a plane to fly around the world = 24,901/561 = 44.38 hours.

The above flight time is just an approximate number because the time required to fly around the world depends on several factors such as
Type of plane: we know that the speed and range of different planes are different. For example, passenger planes such as Boeing 747 flies with an average speed of 570 miles per hour. Therefore, assuming refueling is not required, the Boeing 747 plane will take around 43.68 hours to fly around the world. But if we consider one of the fastest aircrafts such as the Lockheed SR-71 Blackbird in the world, it will take only 11.35 hours to fly around the world because Black Bird can fly at the speed of 3,530 km/h (2194 mph).

Apart from the speed of the plane, if we consider refueling is required, the time required to fly around over the equatorial circumference of the earth will vary with the travel range of the plane. For example, the Lockheed SR-71 Blackbird has a capacity of 12,219 gallons (46,254 liters) with a travel range of 5371 km (2,900 Nautical Miles) while Boeing 747 has a massive fuel capacity of 48,445 gallons (183,380 liters) which allows it to travel 5,000 nautical miles (9,300 km).
Route of the plane: In the above calculation, we have considered that the plane will fly over the equatorial circumference of the earth. However, the traveling time to fly varies with different routes. For example, the traveling time for planes passing from the North Pole to the South Pole will vary as compared to the traveling time over the equatorial circumference because of change in the gravitation field, and atmospheric conditions. You will be surprised to know that it takes longer to fly from east to west than vice versa because of the resistance of the atmospheric jet stream which blows from west to east.
Number of stops: If we are considering refueling the plane, then we have to think about the refueling spots such that the number of pit stops should be less for the plane.
As we know now that there are so many factors involved to calculate the accurate traveling time for a plane to fly around the earth.

By simplifying the calculations with the help of a few assumptions, a plane will take approximately 44 to 45 hours to fly around the world.