I was a Park Ranger assigned in law enforcement at Glen Canyon National Recreation Area (Lake Powell). On the night of 6/29/1981 a gentleman called the Wahweap District Ranger Office and requested a Ranger meet him at the Wahweap launch ramp. A Ranger responded and took this formal Department of Interior, National Park Service, Case Incident Report. The incident was given Case Incident Number 811310.The gentleman reported, that two nights earlier, his group of 15 individuals from Salt Lake City, Utah were camping in Cow Canyon, in the Escalante River Arm, of Lake Powell. The group were all members of the LDS Church and there was absolutely no use of alcohol, or drugs on the trip. The group had a houseboat, that was used as a base, for the trip.NOTE: The following account is taken directly and verbatim from the National Park Service Case Incident Report Number 811310. I have used quotation marks for all information taken verbatim from the Case Incident Report. Where I have used the word "NAME" I have left out the name of the person who gave the account of the incident, to the National Park Service. I have corrected some obvious spelling errors that were in the original account and I have put in brackets ( ) information that can clarify the report, to persons reading it. "On 06-29-81, at approximately 1715 Hrs.(5:15 p.m.), recieved a call from a visitor wanting to report a strange experience in the Escalante River. I contacted NAME at approx. 1745 Hrs.(5:45 p.m.), on the launch ramp (Wahweap launch ramp). On 06-27-81, at approximately 2230 Hrs. (10:30 p.m.), NAME and 14 other persons in his group were camped in Cow Canyon, a side canyon off the Escalante (Escalante River arm of Lake Powell)."Name" was about to tell the group a story of an incident his family experienced five years earlier in Explorer Canyon, which is the next canyon south of Cow Canyon, when the same experience began to happen again. A bright light, which was described to be flashing at 2-4 second intervals, was coming down the left side of the canyon in midair. It circled above the group and then flew down the right side of the canyon. The light was described to be similar to a strobe light and bright enough to light up the canyon wall. The group observed the light flying in close proximity to their campsite for approximately one and a half (1 1/2) hours. At one point it (the object) was thirty (30) feet away when group member shined a spot light on it and described what he saw as "creature-like." Further details include: "winged and larger than a bat." NAME then stated that another light appeared and seemed to flash a signal which was answered by the original light. Both lights then disappeared down the middle of the canyon. NAME stated that this experience was very similar to the one five (5) years ago in Explorer Canyon, only the light was brighter. No alcohol was consumed by any member of the group that night. Cleared 1800 Hrs. (6:00 p.m.)." To me this is an amazing report. The individual making the report did not want his name used and wanted no publicity for himself. The length of time (i.e. 1 1/2 hrs.) that the object was observed, is in itself remarkable and I have not heard of any other report of this duration.During the summer of 1981 the National Park Service received a number of reports, from visitors, camped on the shoreline of Lake Powell, of "giant fireflys." Several of the reports were recieved at the Carl Hayden Visitor Center,located near Glen Canyon Dam. At first the National Park Service, staff members, thought the campers were seeing the strobe lights on the stacks of the Navajo Generating Station, southeast of Page, Arizona. These lights can be seen for miles but some of the campers were in canyon locations, where the power plant stacks could not be seen. It is possible that the sightings of "giant fireflys" were what the group of 15 saw on the night of 6/27/1981.There was a second verbal report given to the Bullfrog District Ranger about a similar sighting to the 6/27/1981 one. The second report was not documented unfortunately but occured two, weeks after the 6/27/1981 report. The individuals who made the second report, were supposed to be on Lake Powell for a week, on a houseboat. The first night out of Bullfrog, Utah, where they rented the houseboat, they camped in Cow Canyon, the same canyon as the 6/27/1981 sighting. The second sighting was very similar to the first sighting. The second group were so disturbed by what they saw, that they returned to Bullfrog Marina, the following morning and turned in their houseboat and said "we are getting the hell out of here," after describing what had happened to them.I have a kept a copy of the original Case Incident Report over the years because of the unusual nature of the UFOs observed. I did submit a copy of this case incident to the Aerial Phenomenon Research Organization in Tucson and they thought it was a most interesting sighting.