The network will be switched off if administrators of the bankrupt Internet services company find that insufficient customers have paid their bills and an advance on June fees.
Customers originally had until close of business yesterday to pay up to keep the network running through June. Keeping the network running would give customers more time to look for an alternative carrier, while the trustees have more time to find a buyer and maximise proceeds for the creditors.
Finnish-based IT services company TietoEnator uses KPNQwest's backbone to connect its offices in 10 countries and had not paid by late Monday afternoon, said Jüri Tuks, chief information officer.
"We are still a customer, even though they want to throw us out. They say that if I pay in advance that I can have a service guarantee for June. We have to let our lawyer look at it first. I am not interested in paying for something that I can only have for a week," he said, adding that TietoEnator has a fallback solution and is looking at a new primary supplier.
Customers underestimate the effect of a network shutdown, according to Graham Kinsey, who manages the Ebone network from an operations centre in Brussels. KPNQwest acquired Ebone last year.
"The biggest corporations are the ones that do not believe that Ebone will go down. They don't really appreciate how close we are to shutting down. Any company that has no backup will go down," he said. "Some customers may have a fallback provider, but it may not be sufficient."
Kinsey, together with several other Ebone staff, has been volunteering to keep the Ebone network up since they were laid off last week, he said.
The impact of a KPNQwest and Ebone network shutdown will ripple far beyond the direct customers, according to Kinsey.
"If KPNQwest goes down it will mean a slowdown of the European Internet generally," he said. "There has never been a network the size of KPNQwest to shut down overnight; nobody really has any perception what it will mean."
KPNQwest, which was worth £27bn during the dotcom boom boom, went bankrupt in late May after a plan to sell some assets to meet its most urgent financial obligations failed.