The National Hockey League is threatening to lock out its players if a new collective bargaining agreement is not in place by Sept. 15.

While the players and their association are offering what they say is an alternative view of the league's economics in the hopes of resolving their multimillion-dollar differences with owners, the differences are such that some observers say a lockout seems inevitable.

If so, it would be the second such NHL work stoppage in a decade, and just the latest in a series of interruptions to halt North American pro sports seasons over the past 25 years.

Money — and how to share it — has, not surprisingly, been the point of conflict. Some of the longer stoppages have not only shortened seasons, they've changed the way revenues are shared and, in some cases, cost their leagues significant goodwill with fans.

Here's a look at five high-profile North American sports disputes.

2011 NBA lockout

After a 149-day lockout, players and owners agreed to the framework for a new 10-year collective bargaining agreement in November 2011.

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Miami Heat forwards Chris Bosh, left, Udonis Haslem, centre, and James Jones chat during a voluntary basketball workout in Miama on Dec. 1, 2011, the first day players could return to team facilities after the NBA lockout began July 1. (Wilfredo Lee/Associated Press)

The deal paved the way for a shortened, 66-game season that began on Christmas Day. It was the second shortened NBA season — the first was a 50-game season in 1998-99, following a lockout then that was supposed to have resolved revenue sharing for the long term.

The current 10-year deal promises owners savings of perhaps $250 million a year in player compensation, but largely leaves intact the soft salary cap system that the players fought hard to maintain.

The deal also includes an expanded revenue sharing plan that could perhaps quadruple the money shared by teams.

2004-05 NHL lockout

The lockout dragged on for 301 days, becoming the longest in North American professional sports history.

It wiped out an entire season — another North American first — and also meant that for the first time since 1919, when the Spanish flu was running rampant, the Stanley Cup was not handed out.

The deal gave owners "cost certainty" and put a salary cap on what teams could spend on players' salaries. Players had argued against a cap, and that pay should be determined through a free market system.

Rules changes brought the shootout, faster play and higher scores.

1994-95 MLB strike

Again, the main issue was a salary cap, and again, another major championship was lost in a dispute that cost baseball players millions, management about $1 billion and alienated millions of fans.

The strike — the eighth stoppage for major league ball — lasted for 232 days and meant that for the first time since 1904, the World Series was cancelled.

The ultimate settlement — which didn't come until 1997 — brought about important changes in the sport's economics by introducing revenue sharing among the 30 teams and a luxury tax meant to slow payroll growth for high-revenue teams.

1994-95 NHL lockout

A 104-day lockout, which cost the league its 1995 All-Star game, ended with a deal that introduced a rookie salary cap, but no overall salary cap, and ultimately sowed the seeds for the lockout a decade later.

Instead, players and owners agreed on a complex system that put greater limits on free agency and on how soon a player could become an unrestricted free agent.

Salary arbitration was also altered. Under the terms of the new deal, players would have fewer rights and the arbitrator rulings would be non-binding, which meant teams who disagreed with the ruling could walk away.

1987 NFL strike

The 1987 NFL players' strike wasn't the longest of disruptions  — it only lasted 24 days — but it was, in the words of Time magazine, "one of the more bizarre stoppages in history."

At its heart was free agency, and the dispute saw owners cobbling together replacement teams after the players called a strike following the second week of the season.

"For three weeks, the likes of what would become known as the Los Angeles Shams, Chicago Spare Bears, Seattle Sea Scabs, New Orleans Saint Elsewheres, Miami Dol-Finks and the San Francisco Phoney-Niners took to the field," Time said.

According to Reuters, while the owners "all but broke" the players union, players won off the field, ultimately getting a court victory for unrestricted free agency. The strike also sparked a 2000 Hollywood movie, The Replacements, starring Keanu Reeves and Gene Hackman.

With files from CBC News and The Associated Press