I need to fly from MKE to JRO in early July (date flexible) returning around 23rd of July from DAR to MKE. I need to purchase an economy ticket with cash (fund source policy) but I would like to pay to upgrade to business using cash or preferably miles or a combination. I tried calling KLM to help me book this and they were less than helpful and couldn’t tell me what was upgradeable. Anyone have any advice or strategies on how to do this? I’ve booked flights before but have never been able to upgrade (cash or miles) and really need a better strategy for the 20+hr flights. Thanks in advance.