Since I got back from my vacation, I have been scanning my television screen for signs of a TWA commercial. Frankly, I expect to argue with it, no matter what it says, particularly about punctuality.

TWA took me to Italy last month, 24 hours after it said it would. The plane from Washington to New York left the ground 50 minutes late. The plane from New York to Rome left on the stroke of 7:10 p.m., leaving me and several hundred other Europe-bound passengers shaking our fists at the sky.

I am grave about vacations. This year's was to be a 10: two weeks in Sicily, in a hill-town called Erice, followed by a sojourn in my favorite U.S. hilltown, Antrim, N. H.

On Aug. 8, I was at the airport two hours early for the 5 p.m. departure of Flight 844 for New York. The connection was tight, but I had no fears. The flight to Rome had the same number.

Flight 844 finally got airborne at 5:50. When, mostly not to appear smug as other passengers pressed anxious inquiries, I asked about 844, the stewardess said, "We're their inbound flight -- they have to wait for us." Besides, there would be TWA representatives at the gate to assist us.

We hurled ourselves off the plane just at 7. The only person waiting at the gate was in a KLM uniform. We raced for the international terminal, to Gate 32. It was dark, locked. I spied an opening, and, followed by several other Italophiles, dived for it. Was this the plane for Rome? "Milan," said the stewardess, "and how did you get on?" She shooed us off the premises.

At the TWA counter, there were curses and lamentations, long lines of people weeping softly over Madrid, Athens. The woman in front of me, who was traveling with her five children, had a problem which made me almost ashamed to complain. Her dog, who was, she told me, "neurotic" was somehow aboard 844. I finally switched lines as she and the agent struggled to compose a telex to her husband in Rome advising him to meet the flight, on which his dog, but not his family, would be.

My new agent suggested a flight plan to Frankfort and then, via Lufthansa to Rome, with a fighting chance of making my connecting flight to Sicily. She called up her friend Stewie in baggage, and as a special favor, he got mine on the flight to Frankfort. But as we talked, the Sicily slipped away. The Frankfort plane had a "minor problem" with its air conditioning.

It was back to the drawing board. For all I know, she was rerouting me via Istanbul, but it was all for naught. Stewie had in fact gotten my luggage on the Frankfort bird, and I could but follow it.

As Flight 842 sat on the runway, the captain came on the PA with a most unjargonlike announcement. "We have a minor problem with the engine on the right."

Half an hour later, the engine on the right still had an oil leak, and the captain was saying that, all ground facilities being closed, we would be served our dinner on board and would be eligible for "hotel availability."

While I ate, my German-born seatmate entertained me with a tale of how on her last TWA flight, her luggage had been lost. "It was vinter, and I vas visout boots for two veeks," she told me several times.

We trailed back to the terminal. The air conditioning had been turned off. We fanned ourselves with our useless tickets. I was rebooked on flight 844 for Aug. 9.

At midnight, we were bused to the Kennedy Inn, which seemed out of another era and behind in its vacuuming. I watched a wonderful old Humphrey Bogart movie, "Beat the Devil," which had a stabbing setting -- Sicily.

At 2:15, the phone rang. It was the desk clerk. He thought I was in the wrong room. Was I headed for Frankfort? The idea of explaining it all was too much. "I don't want to talk about it," I said, and hung up.

Promptly at 1 p.m., a good six hours before my new Flight 844 was to go, I was at the airport, in another line. After an hour, I finally met Diane. She was wonderful. "I'm going to speak to Linda about you," she said when she found she didn't have a seat in no-smoking, where I was about to make my long-deferred debut.

For me to speak to Linda required a return to the line and another hour's wait, but it was worth it. I made the Ambassador class. I was alone, a steward named Bob had nothing in the world to do except to watch over me. He was deeply disapppointed that I would not take a cognac.

A happy ending? Not exactly. When I went to the terminal in Rome, the agent said I had no reservation for Sicily. I was on the list for the day before. I spent an anxious hour on the wait-list line, which is far from the ticket counter.

I have just been told that TWA's motto is "You're going to like us."