Pimentel of Brazil said he expects leaders to approve the creation of a development bank, agreement on technical issues might delay any signing at the Durban summit.

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In a statement, Network Rail blamed the delay on "technical issues" that need resolving with Siemens, the company supplying the new signalling system.

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Randy Baseler, vice-president of marketing for Boeing Commercial Airplane Group, says the delay is due to technical considerations.

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However, the company admitted that the new A400M military transport aircraft has been beset with technical problems, forcing it to delay its first flight.

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Each week, the company announced another delay, due to this technical glitch or that.

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Read this case study about how poorly assessing technical risk cost one company millions of dollars and months of delay.

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If Vega should need to delay its flight through this coming week because of technical concerns, it is highly likely it will be asked to stand down for a month or so.

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