If you combine business with pleasure only part of your costs may be deductible. If your trip was primarily for business, then the portion of the travel costs related to business are deductible. This means that the full amount of airfare may be deductible. Meals and lodging for the days spent on business are also deductible.
An airline pilot based in Minneapolis also flew for the National Guard out of Sioux Falls. His family lived in Sioux Falls. He deducted travel costs to that city only when he was required to fly there for Guard Duty. Whether the time spent is primarily for business, it is determined by the facts and circumstances. There is no hard-and-fast rule.
If you are in a combined (federal, self-employment, and state) tax bracket of 30%, you could reduce your taxes up to $300 for every $1,000 of income reduction by deducting business expenses while traveling.