THE RECENTLY CONCLUDED hearings before the National Transportation Safety Board broke down into an argument between McDonnell Douglas and American Airlines over who did what to the DC10 that crashed in Chicago two months ago. This was perhaps inevitable since each corporation is trying to establish the best posture it can for the damage suits that are to come. But the charges and countercharges are doing little for the reputation of the DC10 or the airline industry.

The theme under development seems to be that the construction and maintenance of big airliners is something less than an exact science. That is, no doubt, true. But it is dismaying that the builders and operators of the DC10 are arguing now about design standards, proper maintenance procedures and production line quality-control techniques. Where were they before that engine fell off and the plane crashed last May?

Eventually, the Safety Board will tell us what it believes caused that crash. Unless the FAA was well off the mark in its investigation, that report will be largely redundant and few, if any, additional modifications will be necessary in the hundreds of DC10s that are flying again. If that is so, the Safety Board would do well to focus less on whose mistakes caused this crash - McDonnell Douglas and American have to fight that issue out in court, anyway - and rule on what can be done to ensure that disagreements and questions about the design and maintenance of any airliner are resolved as they arise - and not left to accumulate until after a plane goes down.