Share repurchase programs are typically viewed positively by the market as they often lead to an increase in the stock price. This is due to the reduction in the number of shares outstanding, which can increase earnings per share (EPS) and the value of remaining shares. AerCap's decision to initiate a substantial repurchase program indicates the company's strong balance sheet and belief in its own undervaluation, which could lead to a positive short-term impact on its stock price.