An explosion and crash of a military transport plane in Pakistan that killed Pakistani president Mohammad Zia ul-Haq this week is certain to create new turmoil in a region already torn by war and political unrest.

Also killed in the crash were Arnold L. Raphel, the U.S. ambassador to Pakistan, and Brig. Gen. Herbert M. Wassom, the senior U.S. military attache to Pakistan. Many of Zia's top aides and military commanders also died in the disaster that took the lives of 39 people.No cause of the crash has been determined at this point, but the reports of an explosion certainly raise the question of sabotage.

The sudden vacuum in Pakistan's leadership - Zia was essentially a dictator at the head of a military junta - raises serious problems for Pakistan and its neighbors. For example, Pakistan is home to 3.5 million Afghan refugees and a pipeline for U.S. military aid funneled to the anti-Soviet rebels. What happens, if anything, to that arrangement now?

And an unfriendly India, worried about Pakistan's work on a nuclear bomb, is likely to become ever more jittery with the unexpected disruption of the political scenery.

Even without Zia, the 450,000-man army remains in command. But there will be power struggles between Zia's allies and enemies. Ethnic minorities who have suffered in restless silence may seize this opportunity to raise rebellions of their own.

Despite his being considered a "special friend" of the U.S., Zia could not be classified as a "good guy." He overthrew the democratically elected government of Zulfikar Ali Bhutto in 1977. Bhutto was later hanged.

Bhutto's daughter, Benazir Bhutto, returned to Pakistan in 1986 after two years in exile and has been trying to build a power base to oust Zia, something like Corazin Aquino did in the Philippines.

Elections are scheduled in Pakistan for Nov. 16. Zia had been carefully pulling the strings, but his death introduces a whole new scenario. If what's left of the government tries to cancel those elections, it could lead to riots. If they take place as planned, the outcome has suddenly become anybody's guess.