Automatic flush facilities can be retrofitted to existing systems. The system could also be retrofitted onto existing airliners. Older buildings must be retrofitted with fire escapes. Existing F-15s were retrofitted with these improvements. AIP can be retrofitted into existing submarine hulls by inserting an additional hull section. Older 767s can be retrofitted with the Signature Interior. Like Enhanced LIGO, certain improvements will be retrofitted to the existing Advanced LIGO instrument. Winglets were not included, but they can be retrofitted. Rather expensive, this could also be retrofitted to an existing car. According to DuPont, existing bioethanol plants can cost-effectively be retrofitted to biobutanol production. The first prototype was later retrofitted with these engines. Some, but not all, modifications can be retrofitted onto existing EC225s. Glock pistols cannot be retrofitted to accommodate the ILS. The 737-300 can be retrofitted with Aviation Partners Boeing winglets. Pendulums spread over Europe as existing clocks were retrofitted with them.