The Phabulous F-4 Phantom wins it hands down !
Vietnam
The Vietnam war was the longest war American had fought in. We got involved with the war in 1954 and it ended in 1973. 58,000 Americans were killed in the war and 2-3 million Vietnamese were killed as well.
1. First war fought by the USAF. 2. Worlds first "jet" war.
WW1 (1914-1918) was mankind's FIRST aerial war; airplanes fought airplanes (dog-fights). Korean War (1950-1953) was man's FIRST "Jet" air war; jet airplanes fought jet airplanes (dog-fights). WW1 & Korean War were the only wars of the 20th century ended by an Armistice.
The first Punic war with a staggering 23 year length
American Indian Wars (American Natives) 1622 to 1890.
The Iran-Iraq War 1980-1988, was one of the longest wars fought in that region.
The Hundred Years War, with the English against the French from 1337 to 1453, thus lasting for 116 years.
It was Great Britain.
The USAF F-100 Super Sabre is America's (might even be the worlds) longest serving jet fighter/bomber in sustained combat. The Super Sabre fought in the Vietnam War from about mid-1961 until mid 1971. Approximately 242 were lost during the war.
To the best of my knowledge, the Hundred Years War is still regarded as the longest lasting war. It was fought between England and France in the 14th and 15th Centuries, and it actually lasted about 117 years.
Defining a war in the traditional method, which the conflict was fought against another "COUNTRY" (nation) which had a set government and a national flag, the Vietnam War would be the longest (war against the nation of North Vietnam). Defining war in the broad sense, and not neccessarily fought against a country with a set government and a national flag, then the American Indian Wars (American Frontier Wars) would be America's longest war(s): roughly 1620 until 1890 (ending at the Battle of Wounded Knee).