Read the passage and answer the question:
The invention of the gas turbine by Frank Whittle in England and Hans von Ohain in Germany in $1939$ signalled the beginning of jet transport. Although the French engineer Lorin had visualized the concept of jet propulsion more than $25$ years earlier, it took improved materials and the genius of Whittle and von Ohain to recognize the advantages that a gas turbine offered over a piston engine, including speeds in excess of $350$ miles per hour. The progress from the first flights of liquid propellant rocket and jet-propelled aircraft in $1939$ to the first faster-than-sound (supersonic) manned airplane (the Bell X–$1)$ in $1947$ happened in less than a decade. This then led very rapidly to a series of supersonic fighters and bombers, the first of which became operational in the $1950$s. World War II technology foundations and emerging Cold War imperatives then led us into space with the launch of Sputnik in 1957 and the placing of the first man on the moon only $12$ years later a mere $24$ years after the end of World War II.
Now, a hypersonic flight can take you anywhere in the planet in less than four hours. British Royal Air Force and Royal Navy, and the air forces of several other countries are going to use a single-engine cousin to the F/A–$22$ called the F–$35$ Joint Strike Fighter. These planes exhibit stealthy angles and coatings that make it difficult for radar to detect them, among aviation’s most cutting-edge advances in design. The V–$22$, known as tilt-rotor, part helicopter, part airplane, takes off vertically, then tilts its engine forward for winged flight. It provides speed, three times the payload, five times the range of the helicopters it’s meant to replace. The new fighter, F/A–$22$ Raptor, with more than a million parts, shows a perfect amalgamation of stealth, speed, avionics and agility.
It seems conventional forms, like the Predator and Global Hawk are passé, the stealthier unmanned aerial vehicles (VA Vs) are in. They are shaped like kites, bats and boomerang, all but invisible to the enemy radar and able to remain over hostile territory without any fear of getting grilled if shot down. Will the UAVs take away pilots‟ jobs permanently? Can a computer-operated machine take a smarter and faster decision in a warlike situation? The new free-flight concept will probably supplement the existing air traffic control system by computers on each plane to map the altitude, route, weather and other planes; and a decade from now, there will be no use of radar any more.
How much bigger can the airplanes get? In the '$50$s they got speed, in the „$80$s they became stealthy. Now, they are getting smarter thanks to computer automation. The change is quite huge: from the four-seater to the A$380$ airplane. It seems we are now trading speed for size as we build a new Super-jumbo jet, the $555$ seater A$380,$ which will fly at almost the same speed of the Boeing $707,$ introduced half a century ago, but with an improved capacity, range, greater fuel economy. A few years down the line will come the truly larger model, to be known as $747$X. In the beginning of $2005,$ the A$380,$ the world’s first fully double-decked superjumbo passenger jet, weighing $1.2$ million pounds, may carry a load of about $840$ passengers.
Barring the early phase, civil aviation has always lagged behind the military technologies (of jet engines, lightweight composite materials etc.). There are two fundamental factors behind the decline in commercial aeronautics in comparison to military aeronautics. There is no collective vision of our future such as the one that drove us in the past. There is also a need for a more aggressive pool of airplane design talents to maintain an industry that continues to find a multibillion dollar-a-year market for its product. Can the history of aviation technology tell us something about the future of aeronautics? Have we reached a final state in our evolution to a mature technology in aeronautics? Are the challenges of coming out with the 'better, cheaper, faster' designs somehow inferior to those that are suited for 'faster, higher, further‟? Safety should improve greatly as a result of the forthcoming improvements in airframes, engines, and avionics. Sixty years from now, aircraft will recover on their own if the pilot loses control. Satellites are the key not only to GPS (global positioning system) navigation but also to in-flight communications, uplinked weather, and even in-flight e-mail. Although there is some debate about what type of engines will power future airplanes-lightweight turbines, turbocharged diesels, or both- there is little debate about how these power plants will be controlled. Pilots of the future can look forward to more and better on-board safety equipment.
What is the fourth paragraph of the passage, starting, “How much bigger... .”, about?
- Stealth, speed, avionics, and agility of new aircraft.
- The way aircraft size has been growing.
- Use of computer automation in aircraft.
- Super-jumbo jets that can take more than $500$ passengers.