Astrike is a ceasing of work, a refusal to work, or a refusal to continue to work, until conditions of work are improved.
A worker would go on strike if they found their workplace dangerous to work in, or found that they had too little pay.
A lockout is where an employer closes a place of employment, the suspends work for their employees, or a refusal by an employer to continue to employ employees for the purpose of compelling employees to accept their current working conditions.
A worker may be locked out if they demanded more payment for a job, or if an employer was tired of the employers moaning about their working conditions.
The government can "force" Air Canada and Canada, as both are seen as essential services to the nation's benefit.
Air Canada workers were striking due to Air Canada suspending the jobs of three workers who sarcastically clapped, and heckled the Labour Minister Lisa Raitt.(source: http://www.cbc.ca/news/canada/story/2012/03/23/air-canada-wildcat.html )
Canada Post workers were striking because of Canada Post's modernisation program. The program would of made carriers have to carry more, and work in any conditions, also the sorting facilities would have people working at machines which were twice as fast as the originals.
(source: http://www.cbc.ca/news/canada/story/2011/06/02/f-postal-strike-tips.html )