Ryan and Idzik were dismissed by owner Woody Johnson on Monday morning, less than 24 hours after one of their rare positive displays of the season, a 37-24 win over the Dolphins in Miami.
But that performance masked what had been another desperately poor season for the franchise, who finished the regular season with a 4-12 record and filled bottom place in the AFC East.
Ryan took over as Jets coach in 2009 and led them to the play-offs in his first two seasons, losing to the Indianapolis Colts and Pittsburgh Steelers in successive AFC Championship games.
But the last four seasons have seen the franchise struggle, missing out on the post-season and never posting a better record than 8-8.
Idzik lasted just two seasons after replacing Mike Tannenbaum in 2013. He was heavily criticized this year for questionable personnel decisions in the NFL draft and free agency, most notably the signing of quarterback Michael Vick.
Johnson said in a statement: “After extensive thought and reflection about the current state of our football team, this morning I informed Rex Ryan and John Idzik that they will not be returning for the 2015 season.
“Both Rex and John made significant contributions to the team, and they have my appreciation and gratitude for their efforts and commitment. Over the years, Rex brought the Jets a bold confidence and a couple of great post-season runs, which all of us will remember.
“I am beginning our search for new football leadership, effective immediately, with guidance and support from respected football experts, including Charley Casserly and Ron Wolf, two Super Bowl winners with decades of valuable experience.
“We will consider all options to improve the Jets. Getting the Jets back on track is my top priority, and today???s decisions are important steps towards achieving our goals.”