I think most of us are used to thinking about aircraft in terms of aerodynamic and mechanical factors. What shape, area, etc. are their wings? How powerful are their engines? What's the power-to-weight ratio? How heavily are they loaded? We usually analyze their performance and capabilities in terms of those factors.
Thus, I was taken aback by this sentence in a report yesterday.
... in 1960, software accounted for 8% of the functionality in the McDonnell Douglas F-4 Phantom, compared with 80% of the functionality in the Lockheed Martin F-22 Raptor in 2010, according to research published in the Air and Space Power Journal.
There's more at the link, which discusses ways to avoid cost overruns on a sixth-generation fighter project.
Intrigued, I looked for the source of that research. It can be found in the papers presented at the 2018 Professional Development and Training Workshop of the International Cost Estimating and Analysis Association. That's a heck of a mouthful, but it's apparently a very authoritative body. The paper in question is this one (link is to an Adobe Acrobat document in .PDF format):
Estimating Future Air Dominance
Methods & Models Track (MM08)
Estimating the cost of aircraft programs early in development presents special challenges. The process requires a consideration of the content of the program and various methods to be employed. The Air Force Cost Analysis Agency recently provided cost advice to the Scientific Advisory Board on how aircraft programs are estimated, recent historical experience/lessons learned, and approaches to reduce life cycle costs while the program is in the conceptual design stage.
There's also a set of Powerpoint slides from his presentation (again, in .PDF format).
I'm not going to quote any of that very technical, involved paper here; but if military and/or aerospace matters are of interest to you, it's worth reading.
I knew that computers were indispensable in modern warfare; but to think that the USAF's premier fighter is dependent on them for 80% of its functionality and, hence, effectiveness . . . that was an eye-opener. Effectively, you can now design the most aerodynamically perfect, most mechanically sound aircraft in existence, and still find it worse than useless in combat if you don't have good sensors and computers to guide your weapons. Alternatively, you may be able to use older airframes and/or designs much longer - even in the face of latest-generation aircraft - by greatly improving their electronics and fitting them with modern weapons. That's clearly what Boeing and the USAF are considering with the F-15X proposal. Given the rapid developments in the field of airborne lasers, it may not be inconceivable that something like the F-15 might be flying a century or more after it was first deployed, because its electronics and weapons will make up for its limitations in other areas.
Food for thought.