The research is based on data from only one airline not cross-sectional data across multiple airlines. The title of the article is a reach. The people hunting

The research is based on data from only one airline not cross-sectional data across multiple airlines. The title of the article is a reach. The people hunting for the cheapest plane ticket don't restrict themselves to one airline only. There might be little variation in fare from day to day for one airline but across airlines there can be significant difference, specially on international routes. Last week, I booked a roundtrip flight from Japan to India for next month. The price variation between airlines was 9x for same dates/week while there was little variation less than 10% for different days within a week for same airline.