1140 ET - Concerns about JetBlue's balance sheet are put on the front burner with the Iran ceasefire ending today, Seaport Research Partners analyst Daniel McKenzie says in a research note. If oil prices surge again from increased hostilities with Iran, JetBlue could be forced to boost debt, putting its balance sheet at risk of becoming too indebted, the analysts say. "Shares could ultimately become worthless," they say. The analysts had upgraded JetBlue shares to a buy rating in April based on the assumption that the Strait of Hormuz would open. Now, they're downgrading the shares to a neutral rating. Shares slide 5.7% to $5.33.