FEW REMEMBER IT, but more than 15 years ago the Interstate Commerce Commission predicted theDelaware & Hudson's downfall and the reasons for its demise.

Creation of a unified Consolidated Rail Corp. from the wreckage of the Penn Central and other Northeast railroads, the ICC said in a report to Congress in 1975, would give it so much clout within that region that it could easily take steps that would threaten the viability of both the D&H and the Boston & Maine Railroad.Conrail would have total control of traffic originating in captive markets and would not voluntarily turn it over to competing carriers, the ICC predicted.

Even granting the D&H trackage rights to reach friendly connections would not help much since Conrail, which also would compete for much of the traffic, controlled the quality of service available.

"If Conrail fails to cooperate actively with D&H in the operation of these routes," the agency contended, "D&H's right to operate over them is worth very little."

The ICC report drew little public attention at the time, but developments over the years appear to have borne out many of its predictions.

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MAUNDERINGS WHILE FLYING about the country on a series of trips:

Almost every airline now has pilots who tell passengers how much they appreciate the business. The pilots rarely miss an opportunity to praise the cabin attendants.

Airline systems, however, don't appear to have caught up with the customer service ethic. Recently, for example, a ticket agent thoughtfully suggested that a customer call the airline before heading for the airport because weather was poor at the destination - a hub - and the system was beginning to back up. Two calls were made to the company's main reservation number, and in each case the carrier said the flight was "on time."

At the airport, the sidewalk check-in attendant informed arriving passengers there was a three-hour delay. Perhaps airlines some day will teach the reservation clerks to tell the truth. One annoying experience such as that can undo a lot of expensive training and customer relations work.

Airlines all overbook reservations. Most of the time, the computers do a good job of estimating the percentage of no-shows for each flight. The number of passengers bumped is relatively small.

But, the people who program the computers seem to forget that at certain holiday and vacation peaks, a very high percentage of reservations will, in fact, be claimed. That's why it's so annoying when carriers conduct an auction for volunteers to give up their seats and large numbers of would-be passengers are denied boarding. The computers work; it's the people who program them who don't always do their jobs properly.

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IF CERTAIN WASHINGTON WALLS HAD EARS, they'd no doubt be telling interesting tales about the meetings two rail labor chieftains have been holding as they explore a possible mega-merger that would reshape the labor picture in the industry.

Colleague Howard Abramson, who covers railroads for The Journal of Commerce in Washington, reports that Richard I. Kilroy, president of the Transportation Communications Union, and Fred A. Hardin, chief of the United Transportation Union, met last week for their first face-to-face talks about merging their two groups.

The TCU, which represents much of the industry's clerical staff, is the largest union of non-operating personnel, while the UTU, which represents trainmen, is the largest of the two unions of operating personnel.

Several sources report that the two men are serious about the possibility of a merger and indicate that Geoffrey H. Zeh, president of the Brotherhood of Maintenance of Way Employees, has also expressed some interest in joining forces.