When the B-52 is over 60 years old, and a large number of F-15 Eagles are over 30, it seems surprising that the Air Force is looking to replace a plane that won't even be in service for twenty years until later this year.
However, according to an Air Force News Service article, the Air Force is looking to replace the E-8 Joint Surveillance Target Attack Radar System, which didn't achieve its initial operating capability until December 1997 according to an Air Force fact sheet. This plane is an all-seeing eye that looks for and tracks ground targets, using the AN/APY-7, a 24-foot long synthetic aperture radar, according to a Northrop Grumman data sheet.
So, why is this system, which isn't even old enough to drink, suddenly planned for replacement? The answer is in the airframe.
The E-8, like the E-3 Sentry, is based on the Boeing 707, a jet that first flew just over 59 years ago. With the exception of Omega Aerial Refueling Services, nobody operates this aircraft commercially.
Furthermore, according to a 2015 FlightGlobal.com report, the E-8s were produced by acquiring second-hand 707s. A September 2016 Air Force report noted that those second-hand 707s had as many as 60,000 flight hours before they had been purchased for conversion.
One JSTARS that had to be written off was built in 1967, according to DefenseTech.org.
In other words, these are old airframes and they've had a lot of use – even before the Air Force gave the 16-plane fleet over 1 million flight hours collectively (as of this past September). That is an average of 62,500 flight hours per plane — meaning that some of the E-8 aircraft could have in excess of 120,000 total flight hours.
That's the equivalent of 5,000 days in the air.
What is the Air Force looking towards in replacing the E-8C? The JSTARS recapitalization project is likely to involve a smaller jet. According to a 2014 report by Aviation Week and Space Technology, Northrop Grumman is testing a new JSTARS based off a Gulfstream V business jet.
Boeing's web site is touting a version of the 737 jet as its entry, attempting to partially piggyback on experience with the Navy's P-8 Poseidon.
Reports indicate the Air Force plans to start retiring the JSTARS in 2019.