Watch Now: Report: NFL Optimistic About 2020 Season Despite Positive Covid-19 Tests (2:29)

As the COVID-19 pandemic continues to affect businesses across the globe, the NFL reportedly remains optimistic the 2020 season will go on as scheduled. But there's no denying the league has already taken a toll from the virus, cancelling all in-person workouts through June and preparing as if stadiums will be half-filled or even totally empty this fall.

In light of this unusual offseason and the uncertainty surrounding the games themselves, let's review history to see how the 2020 campaign stacks up with other disrupted NFL seasons. Football has been sidelined before, no doubt, but how often has the NFL actually called off parts of its season? Here's a look back at every major stoppage since the league began play in 1920:

2020

Cause: COVID-19 pandemic

As of now, the NFL remains on track to play a full 16-game season, albeit with unprecedented restrictions pertaining to physical interactions between players, coaches and staff, not to mention game-day attendance, with many teams already planning as if stadiums will at least be at reduced capacity. Even if, somehow, things proceed as planned in September, the league's already wiped out all in-person spring activities and for months banned staff from even entering team facilities. Training camp is expected to start in late July, with preseason to follow, but even those timelines are already in question.

2011

Cause: Lockout

After a failure to negotiate a new collective bargaining agreement (CBA) with the NFL Players Association, team owners imposed a lockout of players, barring them from team facilities starting in March. A lengthy back-and-forth legal battle ensued, and while the NFL ultimately didn't need its contingency plans for a shortened season, the league still had essentially no offseason, with spring workouts cancelled and free agency delayed until the two sides finally struck a deal in late July. The Hall of Fame Game preseason opener was also wiped from the schedule, with players reporting to training camp roughly a month before the start of the season.

2001

Cause: September 11 terrorist attacks

The NFL was one week into its regular season when destruction hit New York City and impacted the rest of the nation. In response, the league postponed Week 2 games to later in the month and essentially shifted the entire rest of the schedule back one week, making Super Bowl XXXVI, between the Patriots and Rams, the first Super Bowl to be played in February.

1987

Cause: Player strike

The last official strike to disrupt the NFL, this marked the fifth time players stepped away from the game in a span of 19 years and famously forced teams to import replacement players. Unhappy with labor negotiations upon the expiration of the 1982 CBA, many players began sitting out in Week 2, prompting the NFL to cancel Week 3 games and then assemble a bunch of castoffs -- some from the recently defunct USFL -- for Weeks 4-6. Because networks still broadcast the games and some big names, like Joe Montana and Doug Flutie, crossed the picket lines to keep playing, the strike ended by mid-October.

1982

Cause: Player strike

Demanding a refined wage scale, the NFLPA led the most disruptive strike in league history starting in September, with player absences forcing the NFL to cancel seven games on its 16-game schedule. Not only that, but the NFLPA also organized, promoted and held its own All-Star Games at RFK Stadium during the strike. Ultimately, a new five-year CBA was struck in November, reshaping future salary negotiations. The NFL resumed play with an expanded 16-team postseason, which culminated with a Washington Redskins Super Bowl win, in which John Riggins -- who played in the NFLPA All-Star Game -- was crowned MVP.

1974

Cause: Player strike

Seeking true free agency for its players, among other labor practices, the NFLPA saw players sit out from July to August. The strike ended early when players opted to pursue their desires in court, but not until many had already missed most of training camp.

1970

Cause: Lockout and player strike

The NFL and AFL were fresh off their official merger, joining to create two conferences and integrate players from both leagues. But since the players union was a "fledgling" operation at the time, overwhelmed in an effort to accommodate the wishes of both AFL and NFL players, league owners reportedly seized control of labor negotiations and briefly locked out players. In turn, the players went on strike in July, then quickly called it off after the NFL threatened to cancel the season. This helped pave the way for the NFLPA to hire its first executive director and legitimize itself as a union.

1968

Cause: Lockout and player strike

Two years into the announced NFL-AFL merger, which wouldn't become official on the field until 1970, players were still being represented by separate associations. With labor negotiations not unfolding as planned, the players began a strike in July, and team owners responded by imposing their own lockout. Two weeks later, the two sides agreed on their first-ever CBA, and both the NFL and AFL held their 14-game seasons as planned.

1944

Cause: World War II

The global war was still a year from concluding as the NFL began its 25th season, and with many players still serving overseas or recovering from wartime efforts, the Pittsburgh Steelers were forced to merge with the Chicago Cardinals, becoming Car-Pitt for a single season. The league also used a 10-game schedule for the second straight year, after the regular season was shortened by a game the year prior.

1943

Cause: World War II

Mass player shortages resulting from the war, which prompted lots of on-field talent to trade their jerseys for military uniforms, forced the NFL to shorten its schedule from 11 to 10 games in order to accommodate the loss of two teams. The Cleveland Rams suspended operations and sat out the season because of a lack of players, while the Steelers and Eagles merged for one year as the "Steagles."