As Continental Airlines pilots seek hefty pay increases, executive salaries at the nation's fifth-largest airline have soared. Chief Executive Gordon Bethune earned $8.6 million in total compensation last year, including $5.6 million from stock options. His 1996 base salary went from $550,000 to $600,000. The figures were included in the proxy statement mailed to shareholders this week for Continental's May 16 annual meeting. President Greg Brenneman had a salary of $535,500 and a bonus of $787,502. He also received $5.05 million from exercising stock options. Len Nikolai, president of the Independent Assn. of Continental Pilots union, said he doesn't begrudge the executives' pay as long as the Houston-based airline's 4,000 jet pilots and 1,000 commuter pilots get their due. Negotiators for the pilots, who are seeking a 38% pay hike, are scheduled to meet Thursday in Washington for a bargaining session with management.