IAM has nearly 500,000 members ( according to them )
And when USAirways workers had an election to choose representation between the Teamsters or the Machinists , they chose the Machinists - a quote from the article:
Machinists Union Wins Election for 4,600 Mechanic and Related at US Airways
Washington, D.C., August 12, 2013 – In a contest overseen by the Nation Mediation Board (NMB), the International Association of Machinists and Aerospace Workers (IAM) today soundly defeated the International Brotherhood of Teamsters (IBT) in an election to represent nearly 4,600 Mechanic and Related employees at US Airways. The IAM received 1,903 votes, or 58 percent of all votes cast in the five-week election, while the IBT received 1,418 votes, less than 42 percent.
“This victory marks an important milestone for the Mechanic and Related group at US Airways,” said IAM Transportation Vice President Sito Pantoja. “By voting for the Machinists Union our members safeguarded their pensions and seniority heading into the merger with American Airlines while rejecting the empty promises of an organization with a history of corruption.”
- International Association of Machinists and Aerospace Workers website
P.S. - I will give the IAM credit. They have went to the XPO terminal nearby and put leaflets on the cars AND stuck around to talk to the employees.
In a similar situation the Teamsters stapled a flyer to the phone pole and took off like a bat out of hell when the terminal manager went out to say hi.