Union leaders expected by the end of last month to tally the votes for or against proposed new labor contracts at Mesaba Airlines, which finally managed to reach tentative agreements with its pilots, flight attendants and mechanics after more than a year of wrangling. All three deals came within a week of a bankruptcy court judge’s decision to bar the groups from striking and within two weeks of his ruling to allow Mesaba to impose its own contract terms. The tentative deals reportedly would slash Mesaba’s total labor costs by 16 percent, but so-called “snap-back” provisions would return compensation to pre-concessionary levels once the company meets certain financial targets.