United Parcel Service Inc. and a union representing about 2,600 pilots who fly for the shipping company said they have moved their contract talks into mediation.

In a joint statement by UPS and the Independent Pilots Association, the two parties said they have requested mediation by the National Mediation Board for their continuing negotiations.

The two groups said they have been negotiating for 21/2 years but haven't yet reached an agreement on scheduling, compensation, pension, scope and benefits.

Corporate shippers are often spooked by labor negotiations because they think it could result in possible slowdowns or interruptions that might delay their packages.

But as last year showed, even when labor talks have gone smoothly, UPS customers hedge their bets. The company's volume growth in the second quarter was a little less than UPS expected, and the company said labor negotiations with the International Brotherhood of Teamsters hindered growth.

United Parcel Service Inc. and its pilot union on Wednesday said they are jointly asking for federal mediation for contract negotiations, which have already lasted more than two years.

The Independent Pilots Association, which represents about 2,600 UPS pilots, and the company said in a joint statement that they have "utilized their best efforts over the past two and a half years of negotiations," but are still at odds on issues including scheduling, compensation, pension, and benefits.

The National Mediation Board will handle negotiations going forward, according to the statement. The board has successfully helped the two parties to come to an agreement on all three contracts between UPS and the IPA since the union was formed at UPS in 1990. The last contract took about two years of federal mediation before it was signed in 2006.

The contract, which became amendable on Dec. 31, 2011, is governed by the Railway Labor Act, which keeps contracts from expiring and workers from striking, until all negotiation processes--including mediation--are exhausted.

UPS is also currently working to wrap up labor negotiations with the International Brotherhood of Teamsters. While a master contract was passed in June by the company's domestic package-delivery employees, several local groups have rejected supplemental agreements that must be reached before the master contract can take effect.