More than 100 members of Delta Air Lines' pilots union picketed outside Minneapolis-St. Paul International Airport's front doors Friday morning in an attempt to heighten the sense of urgency in securing a new contract with the company's management.

The off-duty pilots carried signs emblazoned with one of their key arguments, "Investment grade airline, investment grade pilots." The MSP event was one of eight peaceful picketing demonstrations held Friday at Delta's largest U.S. hubs.

Delta's pilots, represented by Air Line Pilots Association, International (ALPA), are asking for 40 percent compounded raises over the next three years. With the Atlanta-based carrier enjoying record profits in recent years, the pilots also don't want to give up their current level of profit-sharing, something management has suggested trimming in the past.

The pilots' existing contract became amendable at the end of December. A tentative agreement was reached last year between the company and the union's previous leadership, but the pilots voted to reject that proposal over perceived concessions in several of their benefits. The two sides have been meeting with the U.S. National Mediation Board since March.

In advance of the informational picketing events, Delta released a statement assuring customers its operations would not be disturbed by the demonstrations, and that the two parties "are making progress at the negotiations table."

Delta said it has been meeting regularly with the representatives from the pilot union, and that "there is an aggressive schedule planned with the mediators through June and July." Management has previously said it hopes to reach an agreement this summer.

"But while we're making steady progress, there are still tough issues to resolve in order to reach an agreement," said Capt. Steve Dickson, senior vice president of flight operations in his weekly update to Delta pilots. "Our sleeves are rolled up, and I'm encouraged that we will be able to bring this process to a successful conclusion."

About 1,200 of Delta's 12,000 pilots are based at the airline's Minneapolis-St. Paul hub. Delta employs about 9,700 people in the Twin Cities.