The aircraft's proportions are made possible in no small part due to the massive GE9X engines that each put out about 100,000 pounds of thrust. Boeing is also touting 10 percent better fuel efficiency than "the competition," which includes aircraft like the Airbus A350-1000. The 777X series won't have trouble carrying passengers, with the 777-8 hauling 384 people and the 777-9 handling 426. Airbus' rival machines carry between 350 and 410 people.

The 777X doesn't go into service until 2021, when Emirates and other airlines start receiving their aircraft. There will be plenty of tests in between, though. Boeing has three other test aircraft, and it's planning a "comprehensive" series of tests both in the air and on the ground. The company is clearly aware of its tarnished safety image in light of deadly 737 Max crashes, and it wants to reassure everyone that behemoths like the 777X are safe before they start taking everyday travellers.