Carnival shares are trading higher due to the overall strength in cruise stocks. Additionally, the stock received multiple analyst upgrades on Monday, which is a positive signal for investors and can lead to an increase in stock price in the short term.

Carnival plc's stock is trading higher due to the overall strength in cruise stocks. Although the analyst upgrades are specifically for Carnival Corporation, the positive sentiment can also impact Carnival plc's stock price in the short term, as both companies are part of the same industry.