60 years for the B-52

The Boeing B-52 first flew on April 15, 1952. It entered line service in ___; the last one left the production line in October, 1962. And it is still in service and will be for a long time. There are families with three generations of B-52 pilots - example in the quote below.

DEW Line blog at Flight Global

The US Air Force's Global Strike Command is planning on commemorating the 60th anniversary of the first flight of the Boeing B-52 Stratofortress on 15 April. The original event happened on 15 April, 1952, when the YB-52 prototype took to the air over Seattle, Washington. 

Anyways, the B-52 has been in the USAF fleet for so long that there are quite literally generations who have flown the type. One such example is the 23rd Bomb Squadron's 1st Lt Daniel Welch, who is stationed at Minot AFB, North Dakota. His dad and grandfather both flew the eight-engine bomber. 

There is a joke in the USAF that when any given newer type of bomber is retired to the "Boneyard", the last crew who drops off that aircraft to Davis-Monthan AFB in Arizona will be picked up in a B-52. And there is more than a grain of truth to that...
The B-52 has outlived all of its would be replacements. Remember the B-58 Hustler Mach 2+ bomber? Gone. XB-70--it's in a museum in Ohio. FB-111? Those are rotting away in the desert somewhere. And probably so will the B-1 and B-2 when it comes to their turn... (Don't have a crystal ball, just willing to make that bet) 

The USAF is working on a new stealth bomber under a new program called the Long Range Strike-Bomber... 

The Global Strike Command has put together a timeline:
April 15, 1952 - The first flight of the YB-52 Stratofortress will be commemorated with a long-duration flight from AFGSC Headquarters at Barksdale AFB, Louisiana. 

[June, 1955 Entered service at Castle Air Force Base, California Wikipedia] 

Oct. 26, 1962 - Strategic Air Command received the last B-52 from production line. 

June 18, 1965 - Operation Arc Light - The first use of the B-52D Stratofortress as a conventional bomber from bases in the U.S. to Guam to support ground combat operations in Vietnam. 

May 10 through Oct. 23, 1972 - Operation Linebacker - Linebacker was the first continuous bombing effort conducted against North Vietnam since the bombing halt instituted by President Lyndon B. Johnson in November 1968. 

Dec. 18 through 29, 1972 - Operation Linebacker II - This operation saw the largest heavy bomber strikes launched by the U.S. Air Force since the end of World War II. 

Aug. 2, 1994 - B-52's first round-the-world bombing mission.