Over 30 domestic flights to and from Delhi were delayed on Monday, while eight international flights had to be diverted because of the fog that enveloped the Capital in the morning, reducing visibility to less than 200 metres.

According to airport officials, visibility was below the permissible limits under the existing instrument landing system.

Flights in the days ahead, too, will be at the mercy of the weather, as a planned upgrade in the system is expected to be completed only by next winter.

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Of the eight international flights that could not land in Delhi, four were diverted to Mumbai and the others to Jaipur, Kathmandu, Lahore and Karachi.

Normal departures and arrivals in Delhi started only after 10 am. The first Jet Airways departure was flight 9W 901 from Delhi to Kolkata at 10:30 am as against the scheduled time of 06:15 am, a delay of over four hours. The first Jet Airways arrival was flight 9W 301 from Mumbai to Delhi at 10:54 a.m., two hours later than the scheduled time of 08:55 a.m.

Jet Airways also had to divert two early morning flights to Delhi: 9W 921 from Kolkata to Delhi, which was diverted to Jaipur; and 9W 822 from Chennai to Delhi, which was redirected to Lucknow.

Jet also did not operate the 9W 609/610 Delhi-Leh-Delhi, 9W 3303/3304 Delhi-Chandigarh-Delhi and 9W 333/334 Varanasi-Khajuraho-Varanasi flights because of bad weather over north India.

Similarly, Air Sahara had its first flight taking off only at 11:30 am as all its flights were rescheduled. Some of the carrier's flights that were delayed were its Mumbai, Bangalore, Chennai, Lucknow and Kolkata flights.

Meanwhile, Indian Airlines said though 11 of its flights between 5:15 am and 8:30 am were delayed, it operated two flights --- one each to Vadodara and Bangalore --- under the CAT III A ILS on Monday.

As a part of the upgradation of the airport infrastructure, the Airports Authority of India had installed the system in the Delhi airport in December 2001 to allow landing and take-off even under low-visibility conditions. Still, it has not been able to end the delays caused by fog.

In winter, domestic as well as international airlines often reschedule operations to avoid delays. Industry sources said this year some of the international carriers were even contemplating day schedules to avoid fog-related delay.

Delay delays

• Flights will continue to be  at the mercy of the weather, as a planned upgrade in   the instrument-led landing system is behind schedule
• The ILS was installed at Delhi airport in Dec 2001 to allow landing and take-off even in low-visibility
• This year some international carriers are contemplating day flights to avoid fog