INDIANAPOLIS (AP) _ Indiana and its capital city suffered an incalculable loss when a plane collision killed four civic leaders, including a former aide to Vice President Dan Quayle, officials said Monday.

''It's just indescribable,'' said Sen. Richard G. Lugar, R-Ind. ''It's just so overwhelming.''

Gov. Evan Bayh and others credited the men for work over more than a dozen years of helping reshape the image of Indianapolis, which was formerly derided as ''Nap-town'' and ''India-no-place.''

Killed on Friday were Frank McKinney Jr., John Weliever, Michael A. Carroll and Robert V. Welch. Their funerals were scheduled for Tuesday. The two pilots, William R. Mullen and William P. Bennett Jr., also were killed.

The four civic leaders were hailed as innovators in spurring urban development in Indianapolis.

Welch, 64, was a major player in the construction of the Hoosier Dome, which helped attract the Baltimore Colts to Indianapolis. A Democrat, Welch unsuccessfully opposed former Mayor William H. Hudnut for mayor in 1975, but later worked closely under Hudnut's administration to redevelop downtown.

Weliever, 50, restored credibility to the Hoosier Lottery after former director Jack Crawford resigned amid a sex scandal. He willingly assumed the top post when he would have rather returned to this family's car dealership.

McKinney, 53, an Olympic gold medalist in swimming, was behind many downtown renewal projects, including the restoration of bricks in and around Monument Circle.

Carroll, 51, helped acquire funding for the new Indianapolis Zoo and the city's world-class athletic facilities, including the Hoosier Dome, the Indiana University Natatorium and track and field stadium, and the Indianapolis Sports Center.

Lugar, who served two terms as Indianapolis mayor, said Carroll joined the city administration when Lugar was first elected mayor in 1967. When Lugar became a senator, Carroll was his state director.

Carroll later helped Lugar and Quayle, then a senator, put together a unique arrangement of sharing state offices for constituent services.

''He was always on the cutting edge in the transformation of Indianapolis into a great city,'' Lugar said.

The four were headed to Columbus, Ohio, to visit an international floral exhibition when their plane collided with a smaller one shortly after takeoff.

They were studying the marketing and promotion of the exhibit in the hope of finding ways to promote a park on the White River just west of downtown Indianapolis.

''On a local level, this is parallel to the Challenger explosion,'' said Brenda Bush, a spokeswoman for the White River State Park Development Commission.

On Monday, National Transportation Safety Board investigators said it could be nine months to a year before they determine the cause of the accident.