The Denver Broncos are one of the most celebrated franchises in the NFL. After struggling in their early years in the league, the AFC West powerhouse has managed to turn the tide and tally only a handful of losing seasons since the 1980s.

That made the Broncos one of the more successful teams in the entire league. It hasn't been all great for the squad, which suffered traumatic losses that will surely haunt the franchise forever. Here are three key and heartbreaking moments in Denver Broncos history.

vs. Pittsburgh Steelers (2005 AFC Championship Game)

After a brutal loss to the Miami Dolphins to start their season, the Broncos bounced back as seasoned quarterback Jake Plummer led them to a 13-3 record to clinch their first AFC West division title in almost ten years. They were up against back-to-back champions the New England Patriots in the second round of the playoffs where they impressively took out the Pats 27-13. This set a match-up with the Pittsburgh Steelers for the AFC Championship Game in Denver.

The Broncos came out flat as turnovers piled up and they found themselves being dominated by the Steelers and down 24-3 at the half. The deficit was too big for Denver to be able to get back, even with Plummer leading their offense. Ben Roethlisberger and the Steelers went on to win the AFC Championsip match 34-17. Pittsburgh would also eventually win Super Bowl XL later that year.

vs. Baltimore Ravens (2012 Divisional Playoffs)

Before the 2012 season went underway, the Broncos made a huge deal and signed QB Peyton Manning to a five-year $96 million deal. Manning spearheaded his new squad to another 13-3 winning record after claiming 11 straight wins which also gave them the number one seed in the AFC. After a first-round bye, the Broncos were pitted against the Baltimore Ravens in the divisional round of the playoffs.

It was a tight match-up between both squads as they exchanged touchdowns all the way to the 4th quarter. Manning connected on his 3rd touchdown pass which gave the Broncos a 35-28 lead which they would hold on to till the dying moments of regulation. With 30 seconds to go, Ravens signal-caller Joe Flacco threw an incredible 70-yard pass which ended up in the hands of his receiver Jacoby Jones to tie the game and bring the playoff match to overtime. Both squads battled it out as the game would go into double overtime where Denver would bid farewell to another winning season with a Justin Tucker field goal ending the game: 38-35, Baltimore.

vs. San Francisco 49ers (1990, Super Bowl XXIV)

The 1989-1990 NFL Season was mid-way through quarterback John Elway's era with the Broncos. After just missing the playoffs in the 1988 season, the Broncos won 10 of their first 12 games in the 1989 season to finish the regular season with an 11-5 record. Elway struggled in the regular season but rookies like Bobby Humphrey and David Treadwell were there to back him up. It also didn't hurt Denver that veteran receiver Vance Johnson was having himself a career season. Despite his regular season struggles, Elway found his groove and led the Broncos all the way to the Super Bowl to match-up against Joe Montana and the defending champions the San Francisco 49ers.

Both the 49ers offense and defense proved to be too much for the Broncos as they ended up in a 27-3 rut at half time. The Broncos didn't have an answer to Joe Montana as the Super Bowl MVP was seemingly unstoppable, scoring 5 TD's before the 3rd quarter even ended. San Francisco continued to show their class as the defending champions would go on to win Super Bowl XXIV 55-10, handing the Broncos their fourth Super Bowl loss.