NFL fans will be excited for the upcoming season, as most teams will open their stadiums at full capacity. All but two teams have been given permission to have full capacity when the 2021 season begins. The Indianapolis Colts and Denver Broncos are the only two teams that have not yet been cleared to host all of their fans, although they are reportedly working on authorization to fill their stadiums.2020 NFL season allowed a small number of fans into stadiumsThe 2020 NFL season was severely impacted by the COVID-19 pandemic. Most teams were barred from welcoming fans at the start of the campaign. However, as the weeks went by and restrictions eased, a handful of teams opened their doors to spectators.Roger Goodell on a conference call with media, reiterates they expect full NFL stadiums this season. Says 30 teams would currently be allowed to play in front of full capacity crowds, expect the remaining two to get approval in the near future.— Mike Garafolo (@MikeGarafolo) May 26, 2021The number of fans allowed into stadiums increased as the playoffs approached. However, limited attendance for the majority of the season dealt a devastating blow to the finances of NFL teams.Last season, the NFL mandated the use of face masks for spectators who were admitted and, in some stadiums, fans were required to sign a liability waiver. However, it is unclear what safety measures will be in place this season and whether fans will be asked to show proof of vaccination to be admitted into stadiums.The thought of fans packing NFL stadiums this year has me so freaking pumped. Being at a quiet Gillette Stadium last year was one of the strangest experiences and I can't even imagine what that was like for the players.— Raul Martinez (@RaulNBCBoston) May 25, 2021With the schedule for the season announced earlier this month, teams have already released ticket options for fans to purchase.2021 should see a big leap in terms of ticket sales as compared to 2019. According to NFL executive vice president of club business and league events Peter O'Reilly, the season-ticket renewal rate was 90%, while regular ticket sales were up 83% in the 10-day span since the schedule's release when compared to the same timeframe in 2019.Training camps are set to begin for 29 teams from July 27. The remaining three teams -- Dallas Cowboys, Pittsburgh Steelers and Tampa Bay Buccaneers -- will be allowed to open camps earlier.