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Although airline travel statistics abound, it may take a year to determine whether this year's grounding of Boeing's 737 Max aircraft models made much of an overall impact on the airline industry.

According to the FAA's most recent installment of "Air Traffic by the Numbers," which is also called the ATO Fact Book, 2018 saw mixed results as far the growth of air travel. Here are some of the agency's findings, which were published earlier this month:

• The number of passengers flown by air carriers in 2018 increased by 4.8 percent, to 1 billion.
• The number of pilot certificates increased in 2018 by 3.9 percent, to 633,316.
• Flight delays fell in 2018 by 9%, to 260,325.
• Cancellations declined in 2018 by 3.4% to 101,303.

But these statistics fail to take into account the confidence that travelers may have in their airlines given the recent Boeing troubles, or the loss of business spurred by the international grounding of 737 Max models.