In an effort to cut costs, U.S. Postmaster General John E. Potter has asked Congress to allow the federal Postal Service to go to five-day delivery instead of the current six-day system. It would be unfortunate — and would cause headaches for businesses and individuals alike — to lose that extra day of service. But the Postal Service is facing a possible $6 billion deficit this year and should be granted the flexibility to adjust its delivery schedule as necessary.